• Iterating functions: Operate to return values by applying each element in an array.
  • Does not return a new array
    • arr.forEach(callback): Executes the function once for each item in the array, in ascending ordercallback .
    • arr.every(callback): tests whether all elements in an array pass the test of a specified function. It returns a Boolean value.
      • true. The result of each implementation istrue 或 arrIs empty.
      • false. Element exists, and the result isfalse .
    • arr.some(callback): tests whether at least 1 element in the array passes the provided function test. It returns a Boolean value.
      • true. There is an execution fortrueTo return totrue .
      • false. Each implementation isfalse 或 arrIs empty.
    • arr.reduce(callback): Executes a function on each element in the arraycallback(ascending execution) aggregates its results into a single return value.
/** * arr. ForEach (callback): executes the function callback */ forEach item in the array, in ascending order
var array = [ 'a'.'b'.'c' ];
array.forEach(element= > console.log(element));
/** * std a b c */

function square(num) {
    console.log(num, num * num);
}
var num = [ 1.2.3 ];
num.forEach(square);
console.log(num);
/** * std 1 1 2 4 3 9 */
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/** * arr.every(callback): Tests whether all elements in an array pass the test of a given function. It returns a Boolean value. * Note: This method returns true in any case if an empty array is received. */
function isEven(num){
  return num % 2= = =0;
}
var num = [ 2.4.6.8.10 ];
var even = num.every(isEven);
if(even){
  console.log("All the numbers are even.");
}else{
  console.log("Not all numbers are even.");
}
/** * STD all numbers are even */
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/** * arr.some(callback): tests whether at least one element in the array passes the provided function test. It returns a Boolean value. * Note: This method returns false. */ in any case if an empty array is received
function isEven(num){
  return num % 2= = =0;
}
var num = [ 1.2.3.4.5.6.7.8 ];
var someEven = num.some(isEven);
if(someEven){
  console.log("Some numbers are even.");
}else{
  console.log("No number is even.");
}
/** * STD Some numbers are even */
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/** * reduce(): Performs the function callback (ascending execution) on each element in the array to summarize its result into a single return value. */
function add(num1, num2){
  return num1 + num2;
}
var num = [ 1.2.3.4 ];
var sum = num.reduce(add);
console.log(sum);

function concat(str, i) {
  return str + i;
}
var words = [ "I am "."a "."coder " ];
var re = words.reduce(concat);
console.log(re);
/** * std 10 I am a coder */
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  • Returns the value of the new array
    • Arr.map (callback): Creates a new array, the result of which is the return value of each element in the array after calling the supplied function once.
    • Arr.filter (calllback): Creates a new array containing all the elements that pass the function test.
/** * arr.map(callback): Creates a new array, the result of which is the return value of each element in the array after calling the provided function once. */
function addFive(grade){
  return grade += 5;
}
var grade = [ 77.82.88.95.90 ];
var result = grade.map(addFive);
console.log(result);
/** * std [ 82, 87, 93, 100, 95 ] */

var array = [1.4.9];
var map = array.map(x= > x * 2);
console.log(map);
/** * std [ 2, 8, 18 ] */
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/** * arr.filter(callback): Creates a new array containing all elements that pass the function test. */
var words = [ "spray"."limit"."elite"."exuberant"."destruction"."present" ];
var result = words.filter(word= > word.length > 6);
console.log(result);
/** * std [ 'exuberant', 'destruction', 'present' ] */

function passing(num){
    return num >= 60;
}
var grades = [];
for(var i = 0; i <=10; i ++){ grades[i] =Math.floor(Math.random() * 101);
}
var pass = grades.filter(passing);
console.log('The scores of the 10 randomly generated students are:' + grades);
console.log('The passing marks are:' + pass);
/** * 10 students randomly generated by STD are: 30, 25, 77, 12, 74, 34, 41, 61, 57, 49, 92 Passing scores are: 77, 74, 61, 92 */
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Ideas, procedures for reference

  • wangzheng0822: Array

  • MDN

  • Note: Program output compiled by WebStorm