An iterative approach to arrays in JavaScript

//Both accept 3 parameters, respectively: value, position in array, array object itself
var num = [2, 1, 5, 4, 2, 1, 6, 8, 19];
   //every: Returns TRUE if each entry returns True
var a= num.every (function (Item,index,array) {
Return item>5
});
Console.log (a);
 　　 //False

   //filter: Returns an array of true items
var b= num.filter (function (Item,index,array) {
Return item>5
});
Console.log (b);
 　　 //[6, 8, +]

  //foreach: no return value
var c= num.foreach (function (Item,index,array) {
Return item>5
});
Console.log (c);
 　　 //undefined

    //map: Returns an array that consists of return values
var d= num.map (function (Item,index,array) {
Return ' +index+ ' item: ' +item;
});
Console.log (d);
//["No. 0 2", "1th Item 1", "2nd Item 5", "3rd Item 4", "4th Item 2", "5th Item 1", "6th Item 6", "7th Item 8", "8th item"]

  //some: Returns True if any of the entries returns true
var e= num.some (function (Item,index,array) {
Return item>5
});
Console.log (e);
 　   //True

　　

    =================== Merge method
　　
Reduce and reduceright all items of the iterated algebraic group, returning a final value

    reduce is the same as Reducerright, an iteration from the beginning, and an iteration from the back
    Pass in four parameters: the previous item, the current item, the index of the item, the array itself
The    previous prev is the result of the previous function
    var sum=num.reduce (function (Prev,cur,index,array) {
        if (index==1) {
            Return ' +index+ ': ' +cur+ '; ';
        }
        Return prev+ ' +index+ ': ' +cur+ '; ';
    });
    Console.log (sum);
    1th Item: 1, 2nd item: 5, 3rd item: 4, 4th item: 2; 5th item: 1; 6th entry: 6; 7th entry: 8; 8th: 19;

An iterative approach to arrays in JavaScript