ES5/6 array traversal and some common methods

How to traverse an array1 ... for(vari=0;i<arr.length;i++){}------------------------------------------------------------2...arr.foreach (function(Val,index,arr) {console.log (Val,index,arr)//The third parameter is the original array can not be;}) Arr.foreach ((Val,index,arr)={Console.log ( This, Val,index,arr)//The third parameter is the original array can not be;},bind (123))//This pointer will change the arrow function;------------------------------------------------------------3...arr.map (Val,index,arr) ={console.log (Val,index,arr)//The normal need to return a value and return a new array;}) Note: It is generally necessary to have a return without the equivalent of foreach; reorganize the data structure------------------------------------------------------------4...arr.filter (Val,index,arr) ={   returnval.xxx== conditions;//filtering of unqualified elements;})-----------------------------------------------------------5...arr.some (Val,index,arr) ={   //similar to find, an element of an array matches the true}) Let arr= [A]let Newarry= Arr.some ((val,index,arr) ={   returnval==2}) Console.log (Newarry)//true;-----------------------------------------------------------6...arr.every (Val,index,arr) ={   //returns True if the array matches each element}) Let arr= [1,3,5]let Newarry= Arr.every ((val,index,arr) ={   returnVal%2==1}) Console.log (Newarry)//true;-----------------------------------------------------------7...arr.reduce (Prev,now,index,arr) ={  returnPrev+now;//the number and factorial of the array; The first argument represents the previous one, and the second represents the current}) Let arr= [A]let sum= Arr.reduce ((prev,now,index,arr) ={  returnPrev+now;//factorial math.pow (prev,now) Output}) Console.log (sum)//output 6;------------------------------------------------Let arr= [2,2,3]let sum= Arr.reduce ((prev,now,index,arr) ={  returnMath.pow (Prev,now);//factorial Prev**now}) Console.log (sum)//Output:-----------------------------------------------------------8 ... for(let Val of arr) {//Arr.keys ()//array subscript  //arr.entries ()//an item of an array}let arr1=[1,2,3,4]; for(Let a Arr1.keys ()) {Console.log (a)//Result: 0,1,2,3 iterates through the index of the array arr}--------------------------------------------------Let arr2=[1,2,3,4]; for(Let a arr2.values ()) {Console.log (a)//Result: 1,2,3,4 iterates through the values of the array arr}-----------------------------------------------------------

  Extension operators:  ... Let arr= [A]let arr2= [... arr]//ES6Let ARR3 = Array.form (arr)//ES6Let ARR4 = [].call (arr)//ES5--------------------------------------------------------------Array.form: The class array (get a set of elements, arguments) objects to the group, such as UL Li; with the length attribute; Special JSON:let JSON= { 0: "A", 1: "B", 2: "C", Length:3}let newArr2=Array.form (JSON) Console.log (NEWARR2)//["A", "B", "C"] Special string:let str= "STFSSFG"; let arr1= Str.split ("");//ES5Console.log (arr1) let arr2=array.form (str) console.log (ARR2)--------------------------------------------------------------Array.of (); Turn a set of values into a group; let Arr= Array.of ("xx1", "xx2", "xx3") Console.log (arr)//["Xx1", "xx2", "xx3"]--------------------------------------------------------------Arr.find () find out the first eligible array member; return Undefined;let arr= [1,10,20,200,90];let NEWARR= Arr.find ((val,index,arr) ={   returnval>100;}) Console.log (arr)//;--------------------------------------------------------------Arr.findindex () find location; return not found-1; let arr= [1,10,20,200,90];let NEWARR= Arr.findindex ((val,index,arr) ={   returnval>1000;}) Console.log (arr)//-1;--------------------------------------------------------------Arr.fill (filled with something, start position, end position) let arr=NewArry (10); Arr.fill ("Default value", 1,5)--------------------------------------------------------------Arr.includes () determines whether the array contains this value; let arr= [1,2,3,4];let arr1= Arr.includes (2); Cconsole.log (arr1)//true; Boolean value

ES5/6 array traversal and some common methods