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Summary of JS array Array methods

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Oct 26, 2017 am 10:50 AM

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1.ArrayArray method

##Mutatormethod———— — "Mutation method" will change the value of the array itself;
Accessor method --- "Access method" will not change the value of the array itself;
IterationMethod————"Traversal method";

2.
MutatorMethod

①
[ ].push—Function: Add one or more elements to the end of the array, Pass parameters: (single or multiple array elements); Return value: The length of the new array;
```
 //标准用法
 arr.push(el1, el2 ……elN)；
 //合并两个数组
 [].push.apply(arr1, arr2)
```
②
[ ].pop(), Function: Delete the last element, Pass parameters: None; Return value: The deleted element.
```
//标准用法
let a = [1 ,2 ,3 ];
a.pop();//3
```
③
[ ].unshift—Function: Add one or more elements to the beginning of the array, Pass parameters : (Single or multiple array elements); Return value : The length of the new array;
```
 //标准用法
 arr.unshift(el1, el2 ……elN)；
```
④
[].shift() , Function: delete the first element, Pass parameter: None; Return value: deleted element.
```
//标准用法
let a = [1 ,2 ,3 ];
a.shift();//1
```
⑤
[].reverse(), Function: Reverse the position of array elements, Pass parameters: None ;Return value: reversed array.
```
//标准用法
arr.reverse()
```
⑥
[].splice(), Function: Reverse the position of array elements, Pass parameters: ( Index, number to delete [select], element to be added [select]); Return value: An array composed of deleted elements.
```
//标准用法
array.splice(start)
array.splice(start, deleteCount) 
array.splice(start, deleteCount, item1, item2, ...)
```
⑦
[].fill(), Function: Fill an array with a fixed value from the starting index to the ending index All elements within, Pass parameters: (value used to fill array elements, starting index [select], ending index [select]); Return value: modified array .
```
//标准用法
arr.fill(value) 
arr.fill(value, start) 
arr.fill(value, start, end)
//例子
[1, 2, 3].fill(4)            // [4, 4, 4]
[1, 2, 3].fill(4, 1)         // [1, 4, 4]
[1, 2, 3].fill(4, 1, 2)      // [1, 4, 3]
```
⑧
[].sort(),Function: Sort the elements of the array and return the array,pass Parameter : (function to specify the sorting order [optional]); Return value : Arranged array.
```
//标准用法
arr.sort() 
arr.sort(compareFunction)
//例子
var numbers = [4, 2, 5, 1, 3];
numbers.sort(function(a, b) {
return a - b;
});// [1, 2, 3, 4, 5]
```

3.AccessorMethod

[ ].join
—Function: Join all elements of an array (or an array-like object) into a string. , Pass parameters: (Specify a string to separate each element of the array [select]); Return value: A string concatenating all array elements; <pre class='brush:php;toolbar:false;'>//标准用法 var a = [&#39;Wind&#39;, &#39;Rain&#39;, &#39;Fire&#39;]; var myVar1 = a.join(); // myVar1的值变为"Wind,Rain,Fire" var myVar2 = a.join(&#39;, &#39;); // myVar2的值变为"Wind, Rain, Fire"</pre>
[ ].concat
—Function: Concatenate two or more arrays. ,Passing parameters: (Connect arrays and/or values into a new array [select]);Return value: Merged array;<pre class='brush:php;toolbar:false;'>//标准用法 var alpha = [&#39;a&#39;, &#39;b&#39;, &#39;c&#39;]; var numeric = [1, 2, 3]; alpha.concat(numeric); //[&#39;a&#39;, &#39;b&#39;, &#39;c&#39;, 1, 2, 3]</pre>
[ ].slice
—Function: The method returns a shallow copy of a part of the selected array from the beginning to the end (excluding the end) to a new array. , Pass parameters: (Start index [select], End index [select]); Return value: Truncated array; <pre class='brush:php;toolbar:false;'>//标准用法 var fruits = [&#39;Banana&#39;, &#39;Orange&#39;, &#39;Lemon&#39;, &#39;Apple&#39;, &#39;Mango&#39;]; var citrus = fruits.slice(1, 3); //[&#39;Orange&#39;,&#39;Lemon&#39;] //类数组转数组 function list() { return [].slice.call(arguments)} var list1 = list(1, 2, 3); // [1, 2, 3]</pre>
[ ].toString
—Function: Return a string representing the specified array and its elements, Pass parameters: (none);Return value: Converted string; (=[].join())<pre class='brush:php;toolbar:false;'>//标准用法 var monthNames = [&#39;Jan&#39;, &#39;Feb&#39;, &#39;Mar&#39;, &#39;Apr&#39;]; var myVar = monthNames.toString(); // assigns "Jan,Feb,Mar,Apr" to myVar.</pre>
[ ].includes
—Function: Determine whether an array contains a specified value, Pass parameters: (the element to be found); Return value: true or false; <pre class='brush:php;toolbar:false;'>//标准用法 let a = [1, 2, 3]; a.includes(2); // true a.includes(4); // false</pre>
[ ].indexOf
—Function: The first index of a given element can be found in the array, Pass parameters: (element to be found); Return value: Not found -1, index found; <pre class='brush:php;toolbar:false;'>var array = [2, 5, 9]; array.indexOf(2); // 0 array.indexOf(7); // -1</pre>

4.
IterationMethod

—
Function: Each element executes the provided function once, Pass parameters: (callback(current element, index, the array));Return value: None;
```
 //标准用法
 array.forEach(callback(currentValue, index, array){
 //do something
}, this)
```
②
—
Function: Return the array that satisfies the provided test The value of the first element of the function, Pass parameters: (callback(current element, index, the array)); Return value: The element; ([]. findIndex()Return index)
```
 //标准用法
 array. find(callback(currentValue, index, array){
 //do something
}, this)
```
③
—
Function: Create a new array containing All elements of the test implemented by the provided function, Pass parameters: (callback(current element, index, the array)); Return value: Array of the collection of elements that pass the test;
```
 //标准用法
 let arr = array. filter(callback(currentValue, index, array){
 //do something
 }, this)
```
④[ ].map—作用：创建一个新数组，其结果是该数组中的每个元素都调用一个提供的函数后返回的结果。，传参：（callback(当前元素,索引，该数组)）；返回值：一个新数组，每个元素都是回调函数的结果；
```
 //标准用法
 var numbers = [1, 4, 9];
 var roots = numbers.map(Math.sqrt);
 // roots的值为[1, 2, 3], numbers的值仍为[1, 4, 9]
```

⑤[ ].every—作用：测试数组的所有元素是否都通过了指定函数的测试；传参：（callback(当前元素,索引，该数组)）；返回值：true或false；

   //标准用法
   function isBigEnough(element, index, array) {
    return (element >= 10);}
   var passed = [12, 5, 8, 130, 44].every(isBigEnough);// passed is false
   passed = [12, 54, 18, 130, 44].every(isBigEnough);// passed is true

⑥[ ].some—作用：测试数组的某些元素是否都通过了指定函数的测试；传参：（callback(当前元素,索引，该数组)）；返回值：true或false；

   //标准用法
   function isBigEnough(element, index, array) {
    return (element >= 10);}
   var passed = [1, 5, 8, 3, 4].some(isBigEnough);// passed is false
   passed = [2, 4, 18, 13, 4].some(isBigEnough);// passed is true

⑦[ ].reduce—作用：对累加器和数组中的每个元素（从左到右）应用一个函数，将其减少为单个值；传参：（callback(累加器accumulator，当前元素,索引，该数组)）；返回值：函数累计处理的结果；

   //标准用法
   var total = [0, 1, 2, 3].reduce(function(sum, value) {
    return sum + value;
  }, 0);// total is 6

   var flattened = [[0, 1], [2, 3], [4, 5]].reduce(function(a, b) {
    return a.concat(b);}, []);
    // flattened is [0, 1, 2, 3, 4, 5]

⑧[ ].entries—作用：返回一个新的Array Iterator对象，该对象包含数组中每个索引的键/值对；传参：（无)）；返回值：一个新的 Array 迭代器对象；

   //标准用法
   var arr = ["a", "b", "c"];
   var iterator = arr.entries();// undefined
   console.log(iterator);// Array Iterator {}
   console.log(iterator.next().value); // [0, "a"]
   console.log(iterator.next().value); // [1, "b"]
   console.log(iterator.next().value); // [2, "c"]

⑨[ ].values—作用：数组转对象；传参：（无)）；返回值：一个新的 Array 迭代器对象；

   //标准用法
   let arr = [&#39;w&#39;, &#39;y&#39;, &#39;k&#39;, &#39;o&#39;, &#39;p&#39;];
   let eArr = arr.values();// 您的浏览器必须支持 for..of 循环
   // 以及 let —— 将变量作用域限定在 for 循环中
  for (let letter of eArr) {
         console.log(letter);}

参考资料：https://developer.mozilla.org...

1.Array数组的方法

Mutator方法————"突变方法"会改变数组自身的值；
Accessor方法————"访问方法"不会改变数组自身的值；
Iteration方法————"遍历的方法" ；

2.Mutator方法

①[ ].push—作用：将一个或多个元素添加到数组的末尾，传参：（单个或多个数组元素）；返回值：新数组的长度；
```
 //标准用法
 arr.push(el1, el2 ……elN)；
 //合并两个数组
 [].push.apply(arr1, arr2)
```
②[].pop()，作用：删除最后一个元素，传参：无；返回值：删除的元素。
```
//标准用法
let a = [1 ,2 ,3 ];
a.pop();//3
```
③[ ].unshift—作用：将一个或多个元素添加到数组的开头，传参：（单个或多个数组元素）；返回值：新数组的长度；
```
 //标准用法
 arr.unshift(el1, el2 ……elN)；
```
④[].shift()，作用：删除第一个元素，传参：无；返回值：删除的元素。
```
//标准用法
let a = [1 ,2 ,3 ];
a.shift();//1
```
⑤[].reverse()，作用：数组元素颠倒位置，传参：无；返回值：颠倒后的数组。
```
//标准用法
arr.reverse()
```
⑥[].splice()，作用：数组元素颠倒位置，传参：（索引，删除个数【选】，要添加的元素【选】）；返回值：被删除的元素组成的一个数组。
```
//标准用法
array.splice(start)
array.splice(start, deleteCount) 
array.splice(start, deleteCount, item1, item2, ...)
```
⑦[].fill()，作用：用一个固定值填充一个数组中从起始索引到终止索引内的全部元素，传参：（用来填充数组元素的值，起始索引【选】，终止索引【选】）；返回值：修改后的数组。
```
//标准用法
arr.fill(value) 
arr.fill(value, start) 
arr.fill(value, start, end)
//例子
[1, 2, 3].fill(4)            // [4, 4, 4]
[1, 2, 3].fill(4, 1)         // [1, 4, 4]
[1, 2, 3].fill(4, 1, 2)      // [1, 4, 3]
```
⑧[].sort()，作用：对数组的元素进行排序，并返回数组，传参：（指定排列顺序的函数【选】）；返回值：排列后的数组。
```
//标准用法
arr.sort() 
arr.sort(compareFunction)
//例子
var numbers = [4, 2, 5, 1, 3];
numbers.sort(function(a, b) {
return a - b;
});// [1, 2, 3, 4, 5]
```

3.Accessor方法

①[ ].join—作用：将数组（或一个类数组对象）的所有元素连接到一个字符串中。，传参：（指定一个字符串来分隔数组的每个元素【选】）；返回值：一个所有数组元素连接的字符串；
<pre class='brush:php;toolbar:false;'>//标准用法 var a = [&#39;Wind&#39;, &#39;Rain&#39;, &#39;Fire&#39;]; var myVar1 = a.join(); // myVar1的值变为"Wind,Rain,Fire" var myVar2 = a.join(&#39;, &#39;); // myVar2的值变为"Wind, Rain, Fire"</pre>
②[ ].concat—作用：并两个或多个数组。，传参：（将数组和/或值连接成新数组【选】）；返回值：合并后的数组；
```
//标准用法
var alpha = ['a', 'b', 'c'];
var numeric = [1, 2, 3];
alpha.concat(numeric);
//['a', 'b', 'c', 1, 2, 3]
```
③[ ].slice—作用：方法返回一个从开始到结束（不包括结束）选择的数组的一部分浅拷贝到一个新数组。，传参：（开始索引【选】，结束索引【选】）；返回值：截去后的数组；
<pre class='brush:php;toolbar:false;'>//标准用法 var fruits = [&#39;Banana&#39;, &#39;Orange&#39;, &#39;Lemon&#39;, &#39;Apple&#39;, &#39;Mango&#39;]; var citrus = fruits.slice(1, 3); //[&#39;Orange&#39;,&#39;Lemon&#39;] //类数组转数组 function list() { return [].slice.call(arguments)} var list1 = list(1, 2, 3); // [1, 2, 3]</pre>
④[ ].toString—作用：返回一个字符串，表示指定的数组及其元素，传参：（无）；返回值：转化成的字符串；（=[].join()）
<pre class='brush:php;toolbar:false;'>//标准用法 var monthNames = [&#39;Jan&#39;, &#39;Feb&#39;, &#39;Mar&#39;, &#39;Apr&#39;]; var myVar = monthNames.toString(); // assigns "Jan,Feb,Mar,Apr" to myVar.</pre>
⑤[ ].includes—作用：判断一个数组是否包含一个指定的值，传参：（要查找的元素）；返回值：true或 false；
<pre class='brush:php;toolbar:false;'>//标准用法 let a = [1, 2, 3]; a.includes(2); // true a.includes(4); // false</pre>
⑥[ ].indexOf—作用：在数组中可以找到一个给定元素的第一个索引，传参：（要查找的元素）；返回值：找不到-1，找得到索引；
<pre class='brush:php;toolbar:false;'>var array = [2, 5, 9]; array.indexOf(2); // 0 array.indexOf(7); // -1</pre>

4.Iteration方法

①[ ].forEach—作用：每个元素执行一次提供的函数，传参：（callback(当前元素,索引，该数组)）；返回值：无；
```
 //标准用法
 array.forEach(callback(currentValue, index, array){
 //do something
}, this)
```
②[ ].find—作用：返回数组中满足提供的测试函数的第一个元素的值，传参：（callback(当前元素,索引，该数组)）；返回值：该元素；（[].findIndex()返回索引）
```
 //标准用法
 array. find(callback(currentValue, index, array){
 //do something
}, this)
```
③[ ].filter—作用：创建一个新数组, 其包含通过所提供函数实现的测试的所有元素，传参：（callback(当前元素,索引，该数组)）；返回值：通过测试的元素的集合的数组；
```
 //标准用法
 let arr = array. filter(callback(currentValue, index, array){
 //do something
 }, this)
```
④[ ].map—作用：创建一个新数组，其结果是该数组中的每个元素都调用一个提供的函数后返回的结果。，传参：（callback(当前元素,索引，该数组)）；返回值：一个新数组，每个元素都是回调函数的结果；
```
 //标准用法
 var numbers = [1, 4, 9];
 var roots = numbers.map(Math.sqrt);
 // roots的值为[1, 2, 3], numbers的值仍为[1, 4, 9]
```

⑤[ ].every—作用：测试数组的所有元素是否都通过了指定函数的测试；传参：（callback(当前元素,索引，该数组)）；返回值：true或false；

   //标准用法
   function isBigEnough(element, index, array) {
    return (element >= 10);}
   var passed = [12, 5, 8, 130, 44].every(isBigEnough);// passed is false
   passed = [12, 54, 18, 130, 44].every(isBigEnough);// passed is true

⑥[ ].some—作用：测试数组的某些元素是否都通过了指定函数的测试；传参：（callback(当前元素,索引，该数组)）；返回值：true或false；

   //标准用法
   function isBigEnough(element, index, array) {
    return (element >= 10);}
   var passed = [1, 5, 8, 3, 4].some(isBigEnough);// passed is false
   passed = [2, 4, 18, 13, 4].some(isBigEnough);// passed is true

   //标准用法
   var total = [0, 1, 2, 3].reduce(function(sum, value) {
    return sum + value;
  }, 0);// total is 6

   var flattened = [[0, 1], [2, 3], [4, 5]].reduce(function(a, b) {
    return a.concat(b);}, []);
    // flattened is [0, 1, 2, 3, 4, 5]

⑧[ ].entries—作用：返回一个新的Array Iterator对象，该对象包含数组中每个索引的键/值对；传参：（无)）；返回值：一个新的 Array 迭代器对象；

   //标准用法
   var arr = ["a", "b", "c"];
   var iterator = arr.entries();// undefined
   console.log(iterator);// Array Iterator {}
   console.log(iterator.next().value); // [0, "a"]
   console.log(iterator.next().value); // [1, "b"]
   console.log(iterator.next().value); // [2, "c"]

⑨[ ].values—作用：数组转对象；传参：（无)）；返回值：一个新的 Array 迭代器对象；

   //标准用法
   let arr = [&#39;w&#39;, &#39;y&#39;, &#39;k&#39;, &#39;o&#39;, &#39;p&#39;];
   let eArr = arr.values();// 您的浏览器必须支持 for..of 循环
   // 以及 let —— 将变量作用域限定在 for 循环中
  for (let letter of eArr) {
         console.log(letter);}

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