The newly added API interface forEach map filter in Array in ES5 some every indexOf lastIndexOf reduce reduceRight

The newly added API interface forEach map filter in Array in ES5 some every indexOf lastIndexOf reduce reduceRight

var array = [23,48,66,2];

ForEach: loop, traversing array; no return value. Similar to for Loop

array.forEach(function( value, index, array ) {  console.log(value);  return value *  value;} );

Map: ing meaning, ing returns a new array with a returned value; filterArr: returns a new object

var mapArr = array.map(function(value, index, array ){ return value *  value;});

Filter: the meaning of filtering; return value; filterArr: return the new array after filtering

var filterArr = array.filter(function(value, index, array ) {  if ( value > 20 ) {    return true;  }  return false;});

EveryArr: Meaning of each and every item; return value; every: Return boolean true or false;

var everyArr = array.every(function(value, index, array){  if ( value > 1 ) {    return true;  }});

IndexOf: the first is the retrieved value, and the second is the position to be retrieved starting from 0.

console.log(array.indexOf(23,0));

LastIndexOf: the first is the value to be retrieved, and the second is the position to be retrieved starting from arr. length-1.

console.log(array.lastIndexOf(2,10));

// Initial settings Previous = initialValue = 1, current = 2

// The first iterationPrevious = (1 + 2) = 3, current = 3 

// The second iterationPrevious = (3 + 3) = 6, current = 4 

// The third iterationPrevious = (6 + 4) = 10, current = undefined (Exit) 

var reduce = [1,2,3,4].reduce(function(prev, curr, index, array) { console.log(prev +" "+ curr); return prev + curr; });

// Initial settings Index = 3, previous = initialValue = 4, current = 3

// The first iterationIndex = 2, previous = (4-3) = 1, current = 2 

// The second iterationIndex = 1, previous = (1-2) =-1, current = 1 

// The third iterationIndex = 0, previous = (-1 + 1) = 0, current = undefined (Exit) 

var reduceRight = [1,2,3,4].reduceRight(function(prev, curr, index, array) { if ( index == 0 ) { return prev + curr; } return prev - curr; });

console.log(reduceRight);