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[add, delete, modify, and check the array base]

2022-07-25 06:34:00 【If I become a demon, Buddha, I'm a program maniac】 

 Array addition and deletion 
<body>
		<script type="text/javascript">
			// Operation array    Add data    Delete   Copy    lookup 
			var array = [1,2,3];
			// array[array.length]=4;
			// Add at the end of the array   Additional 
			var res = array.push(5);
			console.log(res);// The length of the array returned after appending 
			
			//  Add... To the head of the array 
			res = array.unshift(0);
			console.log(res);// Returns the length of the array 
			console.log(array);
			
			// Delete the first data of the array  
			res = array.shift();
			console.log(res);// Return the first deleted value 
			console.log(array);
			
			// Delete the last bit of the array 
			res = array.pop();
			console.log(res);// Return the last deleted value 
			console.log(array);
			
			//  Delete the element with the specified number of digits  1  2  3
			console.log('--------splice-------------');
			// splice(1,2,10) from 1 No. 1 position starts   Delete 2 Lattice element   And will 10 from 1 Add... At position No 
			res = array.splice(1,2,10);// The result is   Deleted elements 
			console.log(res);
			console.log(array);
			// 1. Just write one parameter   It will be deleted from the specified starting position to the end of the array    Returns the deleted element as an array 
			//  2. Write two parameters    From the specified location   Delete the specified number of elements   And return... As an array 
			//  3. Write three parameters    Start at the specified location   Delete the specified element , And add the new element from the specified starting position     Return deleted elements 
			// var arr = [1,2,3,4,5,6];
			// res = arr.splice(1);
			// console.log(res);
			// console.log(arr);
			
			//  Find elements in an array  indexOf Find the position where the array first appears   If there is a return subscript 
			//  If there is no return -1
			var array = [1,2,3];
			res = array.indexOf(5);
			console.log(res);// -1
			res = array.indexOf(2);
			console.log(res);//1
			var array = [1,2,3,4];
			
			console.log('--------slice-------------');
			// Array truncation   Does not affect the original array 
			res = array.slice(2,3);//2 Is the starting position of interception  3 It's the end position   however 3 Position No. does not include re inside 
			 console.log(res);
			console.log(array);
			
			res = array.slice(1);// from 1 Start intercepting at position No. to the end of the array 
			console.log(res);
			console.log(array);
			console.log('-------- Copy of array -------------');
			// Copy of array 
			res = array.slice();
			 console.log(res);
			console.log(array);
			
			console.log('--------concat-------------');
			// Array connection 
			var arr2=[5,6,7,8];
			res = array.concat(arr2);
			 console.log(res);
			
			res = array.concat();// Realize the copy of the array 
			 console.log(res);
		</script>
		
		
	</body>

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本文为[If I become a demon, Buddha, I'm a program maniac]所创，转载请带上原文链接，感谢
https://yzsam.com/2022/201/202207191650598284.html

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