A static method

  1. Array.isarray (): checks whether it is an Array

  2. Array.from(): Converts a pseudo-array to a true Array

    Note: The pseudo-array must have the length attribute, otherwise it cannot be converted to the true array. How many values does the array have? If the length is greater than the original number of data, the extra part is undefined

    Instance methods

1. Concat: Link arrays become new arrays

let a1 = [1.2.3]; 
let a2 = ['a'.'b'.'c']; 
let a3 = [11.12.13]; 
let arr = a1.concat( a2, a3, 'red'); 
// Return the new array after concatenation;
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(Find an element in an array and return the index if it is found, or -1 if it is not found, and locate the element where it first appeared.)

let arr = ['a'.'b'.'c'.'d'.'a'.'c']; 
arr.indexOf('c'); // The returned index value is2 ;
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(Find the last position of an element in the array and return the index if it was found, or -1 if it was not found)

let arr = ['a'.'b'.'c'.'d'.'a'.'c']; 
arr.indexOf('c'); 
// Returns an index of 5;
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4. Join: Used to join each element of an array into a string

let arr = ['a'.'b'.'c'.'d'.'e'.'f'];
arr.join(The '-'); 
1.After joining together for'a-b-c-d-e-f'String;2.If you want to concatenate the contents of the array, simply arr.join(' '); Can; The results for'abcdef'String;Copy the code

5. Sort: array sort (encoding sort, first letter only)

	let arr = [1.23.6.13.199.28.96]; Formula: (sort from smallest to largest) arr.sort(function (a,b){returna-b }); (sorted from largest to smallest) arr.sort(function (a,b){return b-a });
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The following methods share a sample array

let arr = [1.2.3.4.5.6.7.8.9.10]; // Sample array
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6. Find: Returns the first element in the array that meets the criteria

let refind = arr.find(i= > {
        return i > 5;
        // Default traversal number group, can write condition, directly return the result that meets the condition;
    });
    console.log(refind);
	// The console result is: 6;
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FindIndex: Returns the index of the first element in the array that meets the condition

let refindIndex = arr.findIndex(i= > {
        return i > 5;
        // Default traversal number group, can write condition, directly return the index value of the element that meets the condition;
    });
    console.log(refindIndex);
	// The console result is: 5;
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8. Some: Returns true if one of the elements satisfies the condition, otherwise false

let resome = arr.some(i= > {
        return i > 5;
    // Default traversal number group, can write condition, return Boolean value;* * or * *Copy the code

9. Every: returns true on all elements, otherwise false

let reevery = arr.every(i= > {
        return i > 5;
    // Default traversal number group, can write condition, return Boolean value;
    });
    console.log(reevery);
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10. Filter: Iterates through the filter elements, filters out the elements that meet the conditions and returns them in a new array

let refilter = arr.filter(i= > {
       return i > 5;
    // Default traversal number group, can write conditions, return a new array;
    });
    console.log(refilter);
	// Console result is:
	(5) [6.7.8.9.10]
		0: 6
		1: 7
		2: 8
		3: 9
		4: 10
		length: 5
		__proto__: Array(0)

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11. Map: Iterates over elements, executes a callback for each item, and returns the result in a new array

let remap = arr.map(i= > {
        return i * i;
    // By default, you can write conditions to return the new array after calculation;
    });
    console.log(remap);
	// Console result is:
	(10) [1.4.9.16.25.36.49.64.81.100]
			0: 1
			1: 4
			2: 9
			3: 16
			4: 25
			5: 36
			6: 49
			7: 64
			8: 81
			9: 100
			length: 10
			__proto__: Array(0)

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12. Reduce: Iterate over elements to obtain the sum of all elements

Syntax: reduce ((The sum, the current term) = >{execute code}, initial value)let theSum = arr.reduce((sum, i) = > {
      return sum += i
    }, 0)

	console.log(theSum)
	// The console output is 55

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13. Includes: Determines whether an array contains a specified value. Returns true if it does, false otherwise

        arr.includes(2)  / / return true
	arr.includes(11)  / / returns false
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14. Shift: Removes the first element from an array and returns the value of the first element

<script type="text/javascript">
var arr = new Array(3)
arr[0] = "George"
arr[1] = "John"
arr[2] = "Thomas"

document.write(arr + "<br />")
document.write(arr.shift() + "<br />")
document.write(arr)
</script>
/ / output:
// George,John,Thomas
// George
// John,Thomas

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