How to delete array elements in javascript

Method: 1. Use delete, the syntax "delete arr [delete the subscript of the element]"; 2. Use pop(), the syntax "arr.pop()"; 3. Use splice(), the syntax "arr.splice (starting position, number of deleted items)"; 4. Use the prototype prototype method.

The operating environment of this tutorial: Windows 7 system, JavaScript version 1.8.5, Dell G3 computer.

In JavaScript, besides Object, the Array type (array) is probably the most commonly used type. Arrays in JavaScript are very flexible compared to arrays in other languages. This kind of flexibility has advantages and disadvantages. The advantage is that it is creative and can provide various flexible solutions; the disadvantage is that it is easy to be brainless, because in fact, it is too flexible, and it is so flexible that it is uncontrollable and crazy.

After teasing a few words before, let’s get back to the topic. Here are 5 ways to delete Array elements in JavaScript, namely using the delete keyword, the pop() stack method, the shift() queue method, and splice( ) operation method and prototype prototype method.

delete keyword

JavaScript provides a delete keyword to delete (clear) array elements.

var colors = ["red", "blue", "grey", "green"];
delete colors[0];
console.log(colors); // [undefined, "blue", "grey", "green"]

It should be noted that after using delete to delete an element, the length of the array remains unchanged, but the deleted element is set to undefined.

pop() stack method

The Array object in JavaScript provides a pop() stack method for popping and returning The last item in the array can be used as a deletion to some extent.

The access rule of the stack data structure is FILO (first in, last out). The stack operation adds items to the top of the stack and removes items from the top of the stack. Use the pop() method, which can move Divides the last item in the array and returns that item, and reduces the length of the array by one.

var colors = ["red", "blue", "grey"];
var color = colors.pop();
console.log(color); // "grey"
console.log(colors.length); // 2

It can be seen that when the pop() method is called, the array returns the last item, which is "grey", and there are only two elements left in the array.

splice() operation method

The JavaScript Array object provides a splice() method for performing specific operations on the array. . splice() is probably the most powerful array method. It can be used in many ways. Here we only introduce the method of deleting array elements. When deleting array elements, it can delete any number of items by specifying only 2 parameters: the position of the first item to be deleted and the number of items to be deleted.

var colors = ["red", "blue", "grey"];
var color = colors.splice(0, 1);
console.log(color); // "red"
console.log(colors); // ["blue", "grey"]

It can be seen that when the splice(0, 1) method is called, one item is deleted from the array starting from the first item.

prototype prototype method

You can achieve the purpose of deletion by adding a method to the prototype of Array.

Array.prototype.remove = function(dx) {　　
if(isNaN(dx) || dx > this.length){
　　　　return false;
　　}
　　for(var i = 0, n = 0;
　　 i < this.length; i++) {
　　　　if(this[i] != this[dx]) {　　　　　　
　　　　this[n++] = this[i];
　　　　}
　　}　　this.length -= 1;
};
var colors = ["red", "blue", "grey"];
colors.remove(1);
console.log(colors); // ["red", "grey"]

This method is actually to implement a deletion logic by yourself, and then add the deletion method to the Array prototype object. Then all Array objects in this environment can use this method. Although it is possible to do so, it is not recommended to modify the prototype of a native object in a production application. The reason is simple. If a method is missing in a certain implementation, then adding this method to the prototype of the native object may lead to naming conflicts when the code is run in another implementation that supports this method. And doing so may accidentally cause native methods to be overridden.

shift() queue method

The Array object in JavaScript provides a shift()queue method for popping and returning The first item in the array can also be used for deletion to some extent.

The access rule of the queue data structure is FIFO (first in, first out). The queue adds items at the end of the list and removes items from the front of the list. Using the shift() method, it can Removes the first item in the array and returns it, decrementing the length of the array by one.

var colors = ["red", "blue", "grey"];
var color = colors.shift();
console.log(color); // "red"
console.log(colors.length); // 2

It can be seen that when the shift() method is called, the array returns the first item, which is "red", and there are only two elements left in the array.

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