window.onerror = function(message, url, lineNumber,columnNo,error) {
    var data = {
        "message":message,
        "url":url,
        "error":error.stack
    };
    $.ajax({
        url:"/error/capture",
        type:"post",
        data:data,
        success:function(){
 
        }
    });
    return true;
};

function rnd( seed ){
    seed = ( seed * 9301 + 49297 ) % 233280; //為何使用這三個數?
    return seed / ( 233280.0 );
};

function rand(number){
    today = new Date(); 
    seed = today.getTime();
    return Math.ceil( rnd( seed ) * number );
};

myNum=(rand(5)); 

var rand = (function(){
  var seed = (new Date()).getTime()
  function r(){
    seed = (seed*9301+49297)%233280
    return seed/(233280.0)
  }
  return function(number){
    return Math.ceil(r()*number)
  }
})()

rand = (function(){
  var today = new Date(); 
  var seed = today.getTime();
  function rnd(){
    seed = ( seed * 9301 + 49297 ) % 233280;
    return seed / ( 233280.0 );
  };
  return function rand(number){
    // return Math.ceil(rnd(seed) * number);
    return Math.ceil(rnd() * number);
  };
})();
myNum = (rand(5));

_.intersection([1, 2, 3], [101, 2, 1, 10], [2, 1]);
=> [1, 2]
_.difference([1, 2, 3, 4, 5], [5, 2, 10]);
=> [1, 3, 4]
let a = new Set([1, 2, 3]);
let b = new Set([3, 5, 2]); 

// 并集
let unionSet = new Set([...a, ...b]);
//[1,2,3,5]

// 交集
let intersectionSet = new Set([...a].filter(x => b.has(x)));
// [2,3]

// ab差集
let differenceABSet = new Set([...a].filter(x => !b.has(x)));
// [1]

再把Set轉換為數組即可.
let arr = Array.from(set);
// 或 let arr = [...set];


相同的

a.filter(function(v){ return b.indexOf(v) > -1 })
不同的
a.filter(function(v){ return !(b.indexOf(v) > -1) }).concat(b.filter(function(v){ return !(a.indexOf(v) > -1)}))

getEventListeners($("selector")) 方法以數組對象的格式返回某個元素綁定的所有事件
getEventListeners($("#firstName")).click[0].listener 會返回ID為 firstName 元素綁定的click事件

inspect($("selector")) 會檢查所有匹配選擇器的DOM元素，并返回所有選擇器選擇的DOM對象。例如inspect($("#firstName")) 選擇所有ID是 firstName 的元素，inspect($("a")[3]) 檢查并返回頁面上第四個 p元素。
$0, $1, $2等等會返回你最近檢查過的幾個元素，例如 $0 會返回你最后檢查的元素，$1 則返回倒數第二個

$("img").each(function() {
    if (!this.complete || typeof this.naturalWidth == "undefined" || this.naturalWidth == 0) {
        this.src = "default.png";
    }
});

在input[type=’password’]的前面加上一個隱藏的密碼框即可,且要求是：不能添加id和name屬性

var $body = $("body");
document.title = ‘title’
// hack在微信等webview中無法修改document.title的情況
var $iframe = $("").on("load", function() {
setTimeout(function() {
$iframe.off("load").remove()
}, 0)
}).appendTo($body)

function imgLoad(src){
    var img = new Image();
    if(img.complete){ //從緩存里面取
        callback();
    }else{
        img.onload = function(){ //實際加載完成
            callback();
        }
    }
    img.src = src;
}

function add(x){
    var sum = x;
    var tmp = function(y){
        sum = sum + y;
        return tmp;     
    }
    tmp.toString = function(){
        return sum;
    }
    return tmp
}

Your browser does not support the HTML5 canvas tag.

function getQueryString(url, name) {
    var reg = new RegExp("(^|&|?)" + name + "=([^&]*)(&|$)", "i");
    var r = url.substr(1).match(reg);
    if (r != null) return unescape(r[2]); return null;
} 

function video_loading( $video ){
        $(".video_loading").show();

        var timer = setInterval(function(){
            var currentTime = $video[0].currentTime; // 檢測當前的播放時間

            if( currentTime>0 ){
                $(".video_loading").hide();
                clearInterval( timer );
            }
        }, 100)
    }
    /**
        視頻的播放時間改變時進行的操作
        videoid video標簽的id
        cur 當前播放時間，可以傳入ended參數
        func 回調函數
    */
    videoUpdate : function(videoid, cur, func){
        var myVideo = document.getElementById(videoid);

        if( myVideo ){
            if( typeof cur =="number" ){
                myVideo.addEventListener("timeupdate", function(){
                    if( this.currentTime>=cur ){
                        func();
                        myVideo.removeEventListener("timeupdate", function(){

                        }, false);
                    }
                }, false);
            }else{
                myVideo.addEventListener(cur, function(){
                    func();
                }, false);
            }
        }
    }
    // 第一屏的視頻進行到4秒時，顯示透明圖層以提供用戶操作
    tool.videoUpdate( "video1", 4, function(){
        $(".s1 .overlay").show();
    });

    // 第一屏的視頻結束時，顯示向下滑動提示按鈕
    tool.videoUpdate( "video1", "ended", function(){
        $(".s1 .tip").show();
    });

$(".bcontent").append("
點擊生成二維碼，可在手機端觀看
");
$(".bcontent").on("click", ".qrcode a", function(){
    var $tsp = $(this).next();

    if( $tsp.find("canvas").length ){
        if( $tsp.css("display")=="block" ){
            $tsp.hide();
        }else{
            $tsp.show();
        }
    }else{
        if( self.showing ){
            return;
        }
        self.showing = true;
        $tsp.show().html( "正在生成中..." );
        $.ajax({
            url : "jquery.qrcode.min.js",
            dataType : "script",
            type : "get"
        }).done(function(){
            self.showing = false;
            $tsp.html("");
            $tsp.qrcode({
                render : "canvas",
                width : 176,
                height: 176,
                text : window.location.href
            });
        })
    }
})

// 創建一個額外的a標簽
function parseURL(url) {
    var a =  document.createElement("a");
    a.href = url;
    return {
        source: url,
        protocol: a.protocol.replace(":",""),
        host: a.hostname,
        port: a.port,
        query: a.search,
        params: (function(){
            var ret = {},
                seg = a.search.replace(/^?/,"").split("&"),
                len = seg.length, i = 0, s;
            for (;i
javascript如何添加前置0
function addPreZero(num){
    return ("000000000"+num).slice(-10);
}
html5實現圖片預覽和查看原圖

var upimg = document.querySelector("#upimg");
upimg.addEventListener("change", function(e){
    var files = this.files;
    if(files.length){
        // 對文件進行處理，下面會講解checkFile()會做什么
        checkFile(this.files);
    }
});
// 圖片處理
function checkFile(files){
    var file = files[0];
    var reader = new FileReader();
    // show表示
，用來展示圖片預覽的
    if(!/image/w+/.test(file.type)){
        show.innerHTML = "請確保文件為圖像類型";
        return false;
    }
    // onload是異步操作
    reader.onload = function(e){
        show.innerHTML = "";
    }
}
判斷 x 是否是整數
function isInteger(x) { 
    return parseInt(x, 10) === x; 
}
function add(x, y) {
    return x.toPrecision() + y.toPrecision()
}
console.log(add(0.1,0.2));
function add(num1, num2){
  let r1, r2, m;
  r1 = (""+num1).split(".")[1].length;
  r2 = (""+num2).split(".")[1].length;

  m = Math.pow(10,Math.max(r1,r2));
  return (num1 * m + num2 * m) / m;
}
console.log(add(0.1,0.2));   //0.3
console.log(add(0.15,0.2256)); //0.3756
PhantomJS抓取網頁并將它渲染成圖片
var page = require("webpage").create();
page.settings.userAgent = "WebKit/534.46 Mobile/9A405 Safari/7534.48.3";
page.settings.viewportSize = { width: 400, height: 600 };
page.open("http://m.bbc.co.uk/news/business", function (status) {
    if (status !== "success") {
        console.log("Unable to load BBC!");
        phantom.exit();
    } else {
        window.setTimeout(function () {
            page.clipRect = { left: 0, top: 0, width: 400, height: 600 };
            page.render("bbc-page1.png");
            page.clipRect = { left: 0, top: 600, width: 400, height: 600 };
            page.render("bbc-page2.png");
            phantom.exit();
        }, 2000);
    }
});
復制與粘貼
Email me at matt@example.co.uk

var copyEmailBtn = document.querySelector(".js-emailcopybtn");
copyEmailBtn.addEventListener("click", function(event) {
    // Select the email link anchor text
    var emailLink = document.querySelector(".js-emaillink");
    var range = document.createRange();
    range.selectNode(emailLink);
    window.getSelection().addRange(range);

    try {
        // Now that we"ve selected the anchor text, execute the copy command
        var successful = document.execCommand("copy");
        var msg = successful ? "successful" : "unsuccessful";
        console.log("Copy email command was " + msg);
    } catch(err) {
        console.log("Oops, unable to copy");
    }

    // Remove the selections - NOTE: Should use
    // removeRange(range) when it is supported
    window.getSelection().removeAllRanges();
});
倒計時的JS
 

var time_distance;
var totleTime;
var stop;
function countdownTime(disTime){
    time_distance =disTime;
    totleTime=time_distance;
    showTime();
}
function showTime(){
    time_distance=totleTime;
    var day=0,
    hour=0,
    minute=0,
    second=0;//時間默認值
    if(time_distance > 0){
        day = Math.floor(time_distance / (60 * 60 * 24*1000));
        hour = Math.floor(time_distance / (60 * 60*1000)) - (day * 24);
        minute = Math.floor(time_distance / (60*1000)) - (day * 24 * 60) - (hour * 60);
        second = Math.floor(time_distance/1000) - (day * 24 * 60 * 60) - (hour * 60 * 60) - (minute * 60);
    }
    if (hour <= 9) hour = "0" + hour;
    if (minute <= 9) minute = "0" + minute;
    if (second <= 9) second = "0" + second;
    // 顯示時間 
    $("#time_d").text(day+"天");
    $("#time_h").text(hour+"時"); 
    $("#time_m").text(minute+"分"); 
    $("#time_s").text(second+"秒");
    stop=setTimeout("showTime()",1000);
    totleTime=totleTime-1000;
    if(totleTime<1000){
        $("#time_d").text("活動");
        $("#time_h").text("已經"); 
        $("#time_m").text("結束"); 
        $("#time_s").text("。");
        clearTimeout(stop);
        }
    
}
一個數每隔一秒執行加1并打印出來
var count = (function() {
    var timer;
    var i = 0;
    function change(tar) {
        i++;
        console.log(i);
        if (i === tar) {
            clearTimeout(timer);
            return false;
        }
        timer = setTimeout(function() {
            change(tar)
        }, 1000)

    }
    return change;
})()

count(50)
onerror log
"use strict";
function errorHandler( message, source, lineno, colno, error){
    var errorDiv = document.getElementById("error");
    errorDiv.classList.remove("hide");
    console.log("Error happened, message:", message);
    console.log("On source file: ", source);
    console.log("On line - col: ", lineno, "-", colno);
    console.log("Error:", error);
    try {
        var ua = navigator.userAgent;
        console.log("UA: ", ua);
    } catch (e) {
        console.log("Unable to get UA");
    }
}
window.onerror = errorHandler;
javascript copy

                BBCode
                
            
"use strict";
function addCopyEventListener(url){
    var divs = document.querySelectorAll("div.copyAsText");
    for (var index in divs) {
        if(!divs.hasOwnProperty(index)) {
            continue;
        }
        var div = divs[index];
        var input = div.querySelector("input");
        var btn = div.querySelector("label");
        if (url !== "") {
            var template = input.getAttribute("data-template");
            input.value = template.replace("${url}", url);
        }
        void function(btn, input){
            btn.addEventListener("click", function(){
                if (btn.disabled) {
                    return;
                }
                var res = false;
                try {
                    input.disabled = false;
                    var section = window.getSelection();
                    section.removeAllRanges();
                    input.focus();
                    input.setSelectionRange(0, input.value.length);
                    res = document.execCommand("copy");
                    input.disabled = true
                } catch(e) {
                    res = false;
                }
                if (res) {
                    var origin = btn.textContent;
                    btn.textContent = "Copied!";
                    btn.disabled = true;
                    setTimeout(function(){
                        btn.textContent = origin;
                        btn.disabled = false;
                    }, 2000);
                } else {
                    window.prompt("Copy to clipboard: Ctrl+C, Enter", input.value);
                }
            });
        }(btn, input);
    }
}
addCopyEventListener("");
//https://github.com/imsobear/blog/issues/31
//只需要對相應的元素綁定 mouseenter 的事件，然后響應 selectText() 這個方法就 ok
function selectText (element) {
    var text = element,
        range,
        selection;

    if (body.createTextRange) {
        // IE
        range = body.createTextRange();
        range.moveToElementText(text);
        range.select();
    } else if (window.getSelection) {
        // Others
        selection = window.getSelection();
        range = doc.createRange();
        range.selectNodeContents(text);
        selection.removeAllRanges();
        selection.addRange(range);
    } else {
        return false;
    }
}
把節點列表(NodeList)轉換為數組
var elements = document.querySelectorAll("p"); // NodeList
var arrayElements = [].slice.call(elements); // 現在 NodeList 是一個數組
var arrayElements = Array.from(elements); // 這是另一種轉換 NodeList 到 Array  的方法

var array1 = [1,2,3];
var array2 = [4,5,6];
console.log(array1.push.apply(array1, array2)); // [1,2,3,4,5,6];
JavaScript實現字符串長度截取
 

function cutstr(str, len) {
        var temp;
        var icount = 0;
        var patrn = /[^x00-xff]/;
        var strre = "";
        for (var i = 0; i < str.length; i++) {
            if (icount < len - 1) {
                temp = str.substr(i, 1);
                if (patrn.exec(temp) == null) {
                    icount = icount + 1
                } else {
                    icount = icount + 2
                }
                strre += temp
            } else {
                break
            }
        }
        return strre + "..."
    }
    function $(id) {
        return !id ? null : document.getElementById(id);
    }
  // 用法：如果地址是 test.htm?t1=1&t2=2&t3=3, 那么能取得：GET["t1"], GET["t2"], GET["t3"]
function get_get(){ 
  querystr = window.location.href.split("?")
  if(querystr[1]){
    GETs = querystr[1].split("&")
    GET =new Array()
    for(i=0;i 100) ? "block": "none"
    }
};
backTop("goTop");
    
    
    
    
    
mockjs讓前端開發獨立于后端
    





rand num
function GetRandomNum(Min,Max)
{   
    var Range = Max - Min;   
    var Rand = Math.random();   
    return(Min + Math.round(Rand * Range));   
}   
var num = GetRandomNum(10,100); 
創建XMLHttpRequest對象
function createXHR(){
    if(typeof XMLHttpRequest != "undefined"){
        return new XMLHttpRequest();
    }else if(typeof ActiveXObject != "undefined"){
        if(typeof arguments.callee.activeXString != "string"){
            var versions = ["MSXML2.XMLHttp.6.0","MSXML2.XMLHttp.                       3.0","MSXML2.XMLHttp"],i,len;
            for(i = 0,len=versions.length;i=200 && xhr.status<300) || xhr.status== 304){
            alert(xhr.responseText);
        }else{
            alert("Request was unsuccessful: " + xhr.status);
        }
    }
}
多行文本溢出顯示省略號
var module = document.getElementById("clamp-this-module");
$clamp(module, {clamp: 3});
微信頁面監聽搖一搖事件，并伴有音效


鼠標向下滾動的時候header會消失
//設置下css，加個綠色的背景，明顯
$(".sf-header").css({
    background : "#CFC",
    width: "100%"
});

//
$(document).scroll( function(){
    var me = arguments.callee; //匿名函數可以 通過 arguments.callee 調用自己
    me.doc = me.doc || $(document); //緩存 $(document);
    me.head = me.head || $(".sf-header");
    me.lastTop = me.lastTop || me.doc.scrollTop();
    if( me.doc.scrollTop() < 20 ||  me.doc.scrollTop() > me.lastTop ){
        //向下 或再 頁面頂部，放在 頭部
        me.head.css({ position : "relative" });
    }else if( me.doc.scrollTop() < me.lastTop  ){
        //向上，懸浮
        me.head.css({ position : "fixed" });
    }
    me.lastTop = me.doc.scrollTop();
});
v2ex 的下一主題
window.location. + (Number(document.location.href.replace(/https://www.v2ex.com/t/(d?)/i, "$1"))+1)
window.location.href.substring(23,29) * 1 + 1
location.href=location.href.split(/[/#]/)[4]*1+1 
location.pathname.substring(3)
判斷一個單詞是否是回文
function checkPalindrom(str) {  
    return str == str.split("").reverse().join("");
}
去掉一組整型數組重復的值
let unique = function(arr) {  
  let hashTable = {};
  let data = [];
  for(let i=0,l=arr.length;i
統計一個字符串出現最多的字母
function findMaxDuplicateChar(str) {  
  if(str.length == 1) {
    return str;
  }
  let charObj = {};
  for(let i=0;i= maxValue) {
      maxChar = k;
      maxValue = charObj[k];
    }
  }
  return maxChar;

}
生成斐波那契數組
function getFibonacci(n) {  
  var fibarr = [];
  var i = 0;
  while(i
閉包

var myObject = {
    foo: "bar",
    func: function() {
        var self = this;
        console.log("outer func:  this.foo = " + this.foo);
        console.log("outer func:  self.foo = " + self.foo);
        (function(test) {
            console.log("inner func:  this.foo = " + test.foo);  //"bar"
            console.log("inner func:  self.foo = " + self.foo);
     }(self));
    }
};
myObject.func();

for(var i = 0; i < 5; i++) {
    setTimeout(function() {
        console.log(i);  // 555555
    }, 1000);
}
for(var i = 0; i < 5; i++) {
    (function(i) {
      setTimeout(function() {
        console.log(i);  //0 ， 1 ， 2 ， 3 ， 4 
      }, 1000);
    })(i)
}
function add(num1, num2){
  let r1, r2, m;
  r1 = (""+num1).split(".")[1].length;
  r2 = (""+num2).split(".")[1].length;

  m = Math.pow(10,Math.max(r1,r2));
  return (num1 * m + num2 * m) / m;
}
console.log(add(0.1,0.2));   //0.3
console.log(add(0.15,0.2256)); //0.3756
10 的階乘
console.log((function f(n){return ((n > 1) ? n * f(n-1) : n)})(10));
邏輯與返回第一個是 false 的操作數 或者 最后一個是 true 的操作數
如果某個操作數為 false ，則該操作數之后的操作數都不會被計算
console.log(1 && 2 && 0);  //0
console.log(1 && 0 && 1);  //0
console.log(1 && 2 && 3);  //3
邏輯或返回第一個是 true 的操作數 或者 最后一個是 false 的操作數
console.log(1 || 2 || 0); //1
console.log(0 || 2 || 1); //2
console.log(0 || 0 || false); //false
如果某個操作數為 true ，則該操作數之后的操作數都不會被計算
如果邏輯與和邏輯或作混合運算，則邏輯與的優先級高
if 中，[] 和 {} 都表現為 true
Unicode 編碼轉換
function encodeUTF8(str){
    var temp = "",rs = "";
    for( var i=0 , len = str.length; i < len; i++ ){
        temp = str.charCodeAt(i).toString(16);
        rs  += "u"+ new Array(5-temp.length).join("0") + temp;
    }
    return rs;
 }
 function decodeUTF8(str){
    return str.replace(/(u)(w{4}|w{2})/gi, function($0,$1,$2){
        return String.fromCharCode(parseInt($2,16));
    }); 
 } 
encodeUTF8("中文")
"u4e2du6587"
decodeUTF8("u4e2du6587")
"中文"
//https://segmentfault.com/q/1010000000095710
var decToHex = function(str) {
    var res=[];
    for(var i=0;i < str.length;i++)
        res[i]=("00"+str.charCodeAt(i).toString(16)).slice(-4);
    return "u"+res.join("u");
}

var hexToDec = function(str) {
    str=str.replace(//g,"%");
    return unescape(str);
}
var decodeHtmlEntity = function(str) {
  return str.replace(/&#(d+);/g, function(match, dec) {
    return String.fromCharCode(dec);
  });
};
var str = "JavaScript高级程序设计";
console.log(decodeHtmlEntity(str));//JavaScript高級程序設計
var encodeHtmlEntity = function(str) {
  var buf = [];
  for (var i=str.length-1;i>=0;i--) {
    buf.unshift(["&#", str[i].charCodeAt(), ";"].join(""));
  }
  return buf.join("");
};
var str = "高級程序設計";
console.log(encodeHtmlEntity(str));//高级程序设计

function u2str(text){ 
     return $("
").html(text).text();
}
數組反轉
var test = [
  [1, 0, 4, 3, 2],
  [0, 4, 3, 2, 1],
  [4, 3, 2, 1, 0],
  [3, 2, 1, 0, 4]
];

test.forEach(arr => console.log(reversal(arr)));

// 反轉
function reversal(arr) {
  let len = arr.length;
  // get max
  let max = arr[0];
  let index = 0;
  arr.forEach((v, i) => {
    if (v <= max) return;
    max = v;
    index = i;
  });

  // strat re
  let tmp = arr.reverse().concat(arr, arr);
  let newIndex = len - 1 - index + len;

  return tmp.slice(newIndex - index, newIndex + len - index);
}
var arr = [1, 0, 4, 3, 2];
反轉為
var arr = [2, 3, 4, 0, 1];
chrome console
dir($("selector")) 會返回匹配選擇器的DOM元素的所有屬性 
獲取某個DOM元素綁定的事件 getEventListeners($("#firstName")).click[0].listener

深拷貝 對象和數組
var cloneObj = function(obj){
    var str, newobj = obj.constructor === Array ? [] : {};
    if(typeof obj !== "object"){
        return;
    } else if(window.JSON){
        str = JSON.stringify(obj), //系列化對象
        newobj = JSON.parse(str); //還原
    } else {
        for(var i in obj){
            newobj[i] = typeof obj[i] === "object" ? 
            cloneObj(obj[i]) : obj[i]; 
        }
    }
    return newobj;
};
//jQuery.extend第一個參數可以是布爾值，用來設置是否深度拷貝的:
jQuery.extend(true, { a : { a : "a" } }, { a : { b : "b" } } );
jQuery.extend( { a : { a : "a" } }, { a : { b : "b" } } );


ajax提交2個相同的鍵值
在form表單中有兩個同name名為"tag"，然后在ajax提交的時候直接用serialize進行了序列化
 $.post("url", {
  tags: 7,
  tags: 128,
})
或者
var str="tags=7&tags=128";
$.ajax({
    type:"post",
    url:"http://localhost/",//地址自己改
    data:str,
    async:true
});
精度丟失
str = "{"a":1234567890123456789,"b":1234567890123239}";
str = str.substr(1);
str = str.substr(0,str.length-1);
str.split(",");
arr = str.split(",");
obj = {};
arr.forEach(function(el,index){
    var arr1 = el.split(":");
    //obj[arr1[0]]=""+arr1[1];
    obj[arr1[0]]=(Number.isSafeInteger(arr1[1])?arr1[1]:(""+arr1[1]));
});
console.dir(obj);
var str = "{"a":1234567890123456789, "b": 1234567890123456789, "c": 1234567890123456789}";
var json = JSON.parse(str.replace(/: *(d*?) *(,|})/g, (a, b, c) => `:"${b}"${c}`));
console.log(json);