Commonly used array methods in JavaScript-JS Tutorial-php.cn

some() method

This method checks whether at least one element of the array meets the conditions checked by the parameter function.

<script>
// JavaScript to illustrate 
// lastIndexOf() method 
function isGreaterThan5(element, index, array) {  
    return element > 5;  
}
function func() {
    // Original array  
    var array = [2, 5, 8, 1, 4];
    // Checking for condition in array  
    var value = array.some(isGreaterThan5);
    document.write(value);  
}
func();  
</script>

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Output:

true

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reduce() method

The array reduce() method in JavaScript is used to reduce an array into a single value and for each value of the array (from left to right) and the return value executes a provided function. The function is stored in the accumulator.

<script>
// Original array 
var numbers = [88, 50, 25, 10];
// Performing reduce method 
var sub = numbers.reduce(geeks);
function geeks(total, num) { 
    return total - num; 
}
document.write(sub) 
</script>

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Output:

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map() method

The map() method in JavaScript creates an array by calling a specific function on each element present in the parent array . This is a non-mutating method. Typically, the map() method is used to iterate over an array and call a function on each element of the array.

<script> // Original array 
var numbers = [4, 9, 16, 25]; 
// Performing map method 
var sub = numbers.map(geeks); 
function geeks() {     
return numbers.map(Math.sqrt); 
} 
document.write(sub)

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Output:

2 3 4 5

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every() method

This method checks whether all elements of the array satisfy the given condition, which is provided by the function passed to it as a parameter .

<script>  // JavaScript code for every() function  
function ispositive(element, index, array) {      
return element > 0;  }  function func() {      
var arr = [ 11, 89, 23, 7, 98 ];      
// Check for positive number      
var value = arr.every(ispositive);      
document.write(value);  }  
func();  
</script>

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Output:

true

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flat() method

This method creates a new array containing multiple arrays. Basically create a simple array from an array containing multiple arrays.

<script>
//Original array 
var arr = [ [11, 89], [23, 7], 98 ];
// Performing flat method 
var geeks = arr.flat();
document.write(geeks) 
</script>

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Output:

11，89，23，7，98

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flatMap() method

This method is used to flatten the input array elements into a new array. This method first maps each element with the help of map function and then flattens the input array elements into a new array.

<script>const myAwesomeArray = [[1], [2], [3], [4], [5]]var geeks = myAwesomeArray.flatMap(arr => arr * 10) console.log(geeks);

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Output:

10、20、30、40、50

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filter() method

This method is used to create a new array from the given array consisting only of the parameters in the given array that satisfy the function Consists of those elements that set conditions.

<script>
function isPositive(value) {  
    return value > 0;  
}
function func() {  
    var filtered = [112, 52, 0, -1, 944] 
    .filter(isPositive);  
    document.write(filtered);  
}
func();  
</script>

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Output:

112、52、944

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findindex() method

This method returns the index of the first element in the given array that satisfies the provided test function. Otherwise, -1 is returned.

<script>
var array = [ 10, 20, 30, 110, 60 ];
function finding_index(element) {  
    return element > 25; 
}
document.write(array.findIndex(finding_index));  
</script>

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Output:

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find（）方法

此方法用于获取满足所提供条件的数组中第一个元素的值。它检查数组的所有元素，以及第一个满足条件的要打印的元素。

<script>
// Input array contain some elements.  
var array = [10, 20, 30, 40, 50];
// Function (return element > 10).  
var found = array.find(function(element) {  
    return element > 20;  
});
// Printing desired values.  
document.write(found);  
</script>

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输出：

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fill（）方法

此方法用于使用给定的静态值填充数组。该值可以用于填充整个数组，也可以用于填充数组的一部分。

<script>
// JavaScript code for fill() function  
function func() {
    var arr = [1, 23, 46, 58];
    // Here value = 87, start index = 1 and  
    // and last index = 3  
    arr.fill(87, 1, 3);  
    document.write(arr);  
}
func();  
</script>

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输出：

1，87，87，58

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forEach（）方法

该方法为数组的每个元素调用一次提供的函数。提供的函数可以对给定数组的元素执行任何类型的操作。

<script>  function func() {      
// Original array      
const items = [1, 29, 47];      
const copy = [];      
items.forEach(function(item){          
copy.push(item*item);      });      
document.write(copy);  }  
func();  
<script>

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输出：

1，841，2209

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sort（）方法

此方法用于对数组进行排序。数组可以是任何类型，例如字符串，数字，字符等。

<script>
// Original array 
var numbers = [88, 50, 25, 10];
// Performing sort method 
var sub = numbers.sort(geeks);
function geeks(a, b) { 
    return a - b; 
}
document.write(sub) 
</script>

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输出：

10、25、50、88

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concat（）方法

此方法用于将两个或多个数组合并在一起。此函数不会更改作为参数传递的原始数组。

<script>
// JavaScript code for concat() function  
function func() {  
    var num1 = [11, 12, 13],  
        num2 = [14, 15, 16],  
        num3 = [17, 18, 19];
    document.write(num1.concat(num2, num3));  
}  
func();  
</script>

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输出：

11，12，13，14，15，15，16，17，18，19

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include（）方法

此方法用于知道数组中是否存在特定元素，因此，它返回true或false，即，如果该元素存在，则返回true，否则返回false。

<script>
    // Taking input as an array A  
    // having some elements.  
    var A = [ 1, 2, 3, 4, 5 ];
    // Include() function is called to  
    // test whether the searching element  
    // is present in given array or not.  
    a = A.includes(2)
    // Printing result of function.  
    document.write(a);  
</script>

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输出：

true

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reverse（）方法

此方法用于数组的就地反转。数组的第一个元素变为最后一个元素，反之亦然。

<script>  function func() {      
//Original Array      
var arr = [34, 234, 567, 4];      
document.write("Original array: " + arr);      
//Reversed array      
var new_arr = arr.reverse();      
document.write("<br>Newly reversed array: ");      
document.write(new_arr);  }  
func();  
<script>

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输出：

原始数组：34、234、567、4新反向阵列：4、567、234、34

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