The summary of the--javascript of the front-end development face (III.) __javascript

http://www.jianshu.com/p/988840419605

Related knowledge points

Data types, operations, objects, function, inheritance, closures, scopes, prototype chains, events, REGEXP, JSON, Ajax, DOM, BOM, memory leaks, Cross-domain, asynchronous loading, template engine, front-end MVC, front-end MVVM, routing, modularity, Http, Canvas, JQuery, ECMAScript 2015 (ES6), Node.js, Angularjs, Vue, react ... Title & Answer function memory, judge is not prime.

Method One:
function isPrime1 (n) {
    if (n<=3) {return true}
    else{for
      (var i=2;i<math.sqrt (n); i++) {
        if (n%i==0) {return false;}
      }
      return true;
    }
;
Method Two: Hash
  var isprime2= (function () {//hash
    var hash={};
    return function (n) {
      if (n<=3) {return true}
      else if (hash[n]!==undefined) {return
        hash[n];
      } else{for
        (var i=2;i<math.sqrt (n), i++) {
          if (n%i==0) {return hash[n]=false}
        } return
        hash[n]= true;
      }
    }
) ();

Array to weight

 method one: Var arr1=[1,2,3,2,1,2]; function Repeat1 (arr) {for (Var i=0,arr2=[];i<arr.length;i++) {if (Arr2.indexof (arr[i)) ==-1) {Arr2.push
      (Arr[i]);
}}//(traversal end) return arr2; Method Two: hash function repeat2 (arr) {//traverses each element in the ARR and declares that the hash for (Var i=0,hash={};i<arr.length;i++) {//hash contains
      The current element value is built//if not included, a new element is added to the hash, with the current element value Key,value defaults to 1 if (hash[arr[i]]===undefined) {hash[arr[i]]=1;
    }}//(traversal end)///Convert hash to index: Var i=0;
    var arr2=[];
    For (arr2[i++] in hash);
return arr2; Method Three: Function Repeat3 (arr) {return Arr.sort (). Join (",,"). Replace (/(^|,,) (
  [^,]+) (,, \2) */g, "$1$2"). Split (",,"); } console.log (REPEAT3 (arr1)); 

Insert Sort

var arr=[2,4,1,5,3];
  function Insertsort (arr) {
    //traverse arr each element (I starting from 1)
    for (Var i=1;i<arr.length;i++) {
      //To temporarily save the current element in the variable t
      var t=arr[i];
      var p=i-1;//declares variable p=i-1
      //Loop: (arr[p]>t&&p>=0) {while
      (arr[p]>t&&p>=0) {
     // Assigning the value of P position to p+1 position
        arr[p+1]=arr[p];
        p--;//p--
      }//(Loop end)
      arr[p+1]=t;//Place T in p+1 position
    }//(Loop End)
  }
  Insertsort (arr);
Console.log (String (arr));

Quick sort:

  function QuickSort (arr) {
    //if arr length<=1 if
    (arr.length<=1) {
      return arr;//directly returns arr
    }
    Compute the reference bit P
    var p=math.floor (ARR.LENGTH/2);
    var left=[];
    var right=[];
    Deletes the element of P position
    var center=arr.splice (p,1) [0];
    Iterate through the arr for each element for
    (var i=0;i<arr.length;i++) {
      if (arr[i]>=center) {
        Right.push (arr[i));
      } else{
        Left.push (Arr[i]);
      }
    Return QuickSort (left). Concat (Center,quicksort)
  }
  var sortedarr=quicksort (arr);
  Console.log (String (Sortedarr));

Regular expressions

(1) "Ryan5 is6 not7 A8 good9 man10"
var n=5;
var str= "Ryan is not a good mans";
Str=str.replace (/\b[a-z]+\b/g,function (kw) {return kw+n++;});
Console.log (str);

What is the number of occurrences of each character in the statistics string? The time of the show?

  var str= "HelloWorld";
  Method One: Hash for
  (var i=0,hash={};i<str.length;i++) {
    if (Hash[str[i]]) {
      hash[str[i]]++
    }else{
      hash[str[i]]=1
    }
  }
  Console.dir (hash);
Method Two: Use the regular
var arr=str.split ("")
  . Sort ().
  join ("")
  . Match ([[A-z]) \1*/g
  . Sort (function (a) , b) {return
b.length-a.length;})
Console.log ("appears most is:" +arr[0][0]
  + "altogether" +arr[0].length+ "the Time");
var hash={};
  Arr.foreach (function (val) {
    hash[val[0]]=val.length;
  });
  Console.dir (hash);

Array Dimension Reduction

var arr=[
    [0,0,0,0],
    [0,0,0,0],
    [0,0,0,0],
    [0,0,0,0],
  ];
  Method 1: For
  (var r=0,arr1=[];r<arr.length;r++) {for
    (var c=0;c<arr[r].length;c++) {
      Arr1.push ( Arr[r][c]);
    }
  Console.dir (arr1);
  Method 2: For 
  (var r=0,arr2=[];r<arr.length;r++) {
    arr2=arr2.concat (arr[r]);
  }
  Console.dir (ARR2);
Method 3:
  var arr2=[].concat.apply ([],arr);
  Console.dir (ARR2);

function Assignment

  var f=function () {var a=b=1;}
  f ();
  Console.log (b);//1
  Console.log (a);/error
  var f=function () {var a=b=1;}
  SetTimeout (f,0);
  Console.log (b);//Error
  F ();
  var a,b=0, fn=function () {var a=b=2;}
  fn ();
  Console.log (a);//undefined
  Console.log (b);//2

function currying (Coliward)

  var getn;
  function Add (n) {
    getn=function () {console.log (n);}
    return function (m) {
      n+=m;
    Arguments.callee.tostring=function () {return
        n;
      }
      Return Arguments.callee
    }
  }
  Add (1) (2) (3); GETN ();//6
  Add (1) (2) (3) (4); Getn ();//10
  alert (Add (1) (2) (3));//6
  alert (Add (1) (2) (3) (4));//10

Recursion

var emp={
 work:function () {//3,2,1
  var  sum=0;//+3+2+1 +2+1  +1 for
  (vari=0; i< arguments.length&&arguments[0]>0;
        i++) {
        sum+=arguments[i]
            +arguments.callee (
              --arguments[i]
            );
      }
      return sum;
    }
  Console.log (Emp.work (3,2,1));//10

Closed Bag

 (1) function Fun (n,o) {//outer functions Console.log (o);
      return {fun:function (m) {//inner-layer function n return fun (m,n); }} var a=fun (0); A.fun (1); A.fun (2);
   A.fun (3);
Undefined 0 0 0 var a=fun (0). Fun (1). Fun (2). Fun (3);