Five iteration methods and two merge methods for js arrays recommended by of

2021-06-28 10:40:10
OfStack
Five iteration methods and two merge methods for js array (recommended)

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    //every() Equivalent to Logical AND 
    var arr = [1,2,3,4,5,6,7,8];
    var everyRes = arr.every(function(item,index,array){
        return (item>2);
    });
    alert(everyRes);
    //some() Equivalent to logical or 
    var someRes = arr.some(function(item,index,array){
        return (item>2);
    });
    alert(someRes);
    //filter() Returns an array of given conditions 
    var filterRes = arr.filter(function(item,index,array){
        return (item>2);
    });
    alert(filterRes);
    //map() Returns an array of given conditions 
    var mapRes = arr.map(function(item,index,array){
        return (item*2);
    });
    alert(mapRes);
//forEach() no return value   Interested in self-testing 
 }


    //reduce() Merge method   Accept incoming functions and initial values as merge basis ( Optional 
    // Function Receive To Incoming 4 Functions, first 1 Values, Current Value, Index Item, Array Object 
    var sum = arr.reduce(function(prev,cur,index,array){
       return prev + cur;
    });
    alert(sum);
    //reduceRight() Merge method   and reduce() Method Essence 1 So, the difference is that you start from the back and start from the front. 
    var sum2 = arr.reduceRight(function(pre,cur,index,array){
       return pre + cur;
    });
    alert(sum2);
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