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This article mainly introduces the relevant knowledge of "how to determine the existence of specified elements in an array by JavaScript". The editor shows you the operation process through an actual case. The method of operation is simple, fast and practical. I hope that this article "how to determine the existence of specified elements in an array by JavaScript" can help you solve the problem.

In JS, you can use the some () method to determine whether there are specified elements in the array. This method can detect whether there are elements in the array that meet the specified conditions, return true if they exist, and return the false; syntax format "array.some (callbackfn [, thisArg]);" if they do not exist.

The operating environment of this tutorial: windows7 system, javascript1.8.5 version, Dell G3 computer.

JS some () method: detects whether there are qualified elements in the array

The JavaScript some () method is used to detect whether there are elements in the array that meet the specified conditions, returning true if they exist and false if they do not exist. On the other hand, some () can also be used to check whether all the elements in the array do not meet the specified conditions, returning false if none of them match, and true if there are one or more matches.

The specific usage of some () is as follows:

Array.some (callbackfn [, thisArg])

Parameter description:

Array: required parameter, an array object.

Callbackfn: required parameter, a function that accepts up to three parameters. The some () method calls the callbackfn function for each element in array until callbackfn returns true, or until the end of the array is reached.

ThisArg: an optional parameter for which the this keyword can be referenced in the callbackfn function. If thisArg is omitted, undefined is used as the return false.

The song () method calls the callbackfn function on each array element in ascending indexing order until the callbackfn function returns true. If the element that causes callbackfn to return true is found, the some () method returns true immediately. If the callback does not return true for any element, the some () method returns false.

The some () method does not call the callback function for missing elements in the array. Except for array objects, the some () method can be used by any object that has a length property and has a numerically indexed property name, such as an associative array, Arguments, and so on.

Example:

Detects whether the value of the element in the array is odd. If the some () method detects an even number, it returns true and indicates that it is not all odd; if no even number is detected, it indicates that it is all odd.

Function f (value, index, ar) {if (value% 2 = = 0) {return true;}} var a = [1m15, 4, 10, 10 and 11]; var evens = a.some (f); if (evens) {console.log ("not all odd"). ;} else {console.log ("all odd.") This is the end of the introduction to "how JavaScript determines whether an array has a specified element". Thank you for your reading. If you want to know more about the industry, you can follow the industry information channel. The editor will update different knowledge points for you every day.

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