Common techniques in JS development

From: http://www.cnblogs.com/jone-chen/p/5897829.html
1, get the random number within the specified range 123function getradomnum (min,max) {return Math.floor (Math.random () * (Max-min + 1)) + min;}    2. Randomly get the elements in the array 1234function Getradomfromarr (arr) {return Arr[math.floor (Math.random () *arr.length)];}    3. Generate a numeric array from 0 to a specified value 12345function GetArray (len) {var arr = [],i = 1;    for (; Arr.push (i++) < Len;);    Console.log (arr)} is equivalent to: 1234567function GetArray (len) {var arr = [],i = 1; for (; i < Len; i++) {Arr.push (i)} console.log (arr)}4, disrupting the order of the array of numbers 1234var arr = [1, 2, 3, 4, 5, 6, 7, ' a ', ' Dsfs ', 8, 9, ' V '];arr.sort (function () {return math.random ()-0.5}), 5, object conversion to an array 1234567891011121314//note that the object must be in the following format in order to pass this  The way to convert an array//Gets the DOM collection, and the arguments of the function can also be converted in this way to the array var obj = {0: ' Qian ', 1: ' Long ', 2: ' Chu ', 3: ' Tian ', length: 4}var Objarr = Array.prototype.slice.call (obj);//var Objarr = [].slice.call (obj);//var Objarr = Array.prototype.slice. Apply (obj); Console.log (Objarr) 6, verify that the array 123function IsArray (obj) {return Object.prototype.toString.call (obj) == = ' [Object Array] ';} 7. Gets the maximum or minimum value of 123456function maxandmin (arr) {return {max:Math.max.apply (', ') in the array. Split (', ')), M In:Math.min.apply (' Null,arr.join '). Split (', '))}}8, empty array 1234567891011//by setting the length to 0var arr = [1, 2, 3, 4, 5];arr.leng th = 0; Way two through the splice method var arr = [1, 2, 3, 4, 5];arr.splice (0, arr.length); Way three by assigning an empty array [] to an array (strictly speaking, this simply assigns the ary to an empty array, before the array if there is no reference in point to it will wait for garbage collection.)  ) var arr = [1, 2, 3, 4, 5];arr = [];9, reserved for the specified decimal digit 12var num =4.345678;num = num.tofixed (4); 4.3457 the first four decimal digits are rounded to calculate 10, generate a random alphanumeric string of the specified length 1234567891011121314151617181920//generate a random alphanumeric string of the specified length */* notation a function    Getrandomstr (len) {var str = "";    for (; str.length < len; str + math.random (). toString (. substr (2)); Return str.substr (0, Len);}    Notation two function getrandomstr (len) {var str = ""; for (; str.length < Len;)    {str + = Math.random (). toString (+). substr (2); } return str.substr (0, Len);} *//* three */function getrandomstr (len) {for (var str = '; str.length < Len; StR + = Math.random (). toString (+). substr (2)); Return str.substr (0, Len)}11, find the most frequently occurring element in the array, and give the position where it occurred 123456789101112131415161718192021222324252627function    Getmaxandindex (arr) {var obj = {};            Arr.foreach (function (item, index) {if (!obj[item]) {Obj[item] = {indexs: [index]        }} else {obj[item][' indexs '].push (index);    }    }); var num = 0; Record number of occurrences max var str = '; Record the most occurrences of the character Var Rearr;        Returns the maximum value of the position array for (Var attr in obj) {var temp = obj[attr][' indexs ');            if (Temp.length > num) {num = temp.length;            str = attr;        Rearr = temp; }} return {maxstr:str, Indexs:rearr}}

　　

Common techniques in JS development