javascript null or empty check

You can just check if the variable have a truthy value or not. That meansif( value ) {}Would evaluate to true if are not value : Null Undefined NaN Empty string ("") 0 False The above list represents all possible

A simple method to determine whether the JavaScript Object is null or the property is null First, let's talk about the difference between null and undefined: If typeof is executed on declared but uninitialized and undeclared variables, "undefined"

When discussing the primitive data types in Javascript, most people know the basic knowledge, from String, Number to Boolean. These primitive types are quite simple and behavior is common sense. However, this article will focus more on the unique

This article mainly introduces the Null and Undefined primitive data types in javascript. If you need them, you can refer to the basic knowledge that most people know when discussing the primitive data types in JavaScript, from String, Number to

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When discussing the raw data types in JavaScript, most people know the basics, from String,number to Boolean. These primitive types are fairly simple and behave in a common sense. However, this article will focus more on the unique original data

When discussing the primitive data types in JavaScript, most people know the basic knowledge, from String, Number to Boolean. These primitive types are quite simple and behavior is common sense. However, this article will focus more on the unique

When typeof is executed on declared but uninitialized and undeclared variables, undefined is returned. null indicates a null object Pointer. The typeof operation will return the object. First, the difference between null and undefined is described

Body: For null or empty references, most programming languages have only one value. For example, null is used in Java. However, Javascript has two special values: undefined and null. They are basically the same, but their usage is slightly different.

1. Type Analysis:The data types in js include undefined, boolean, number, string, and object. The first four are original data types and the second are reference data types.Code Copy codeThe Code is as follows: var a1; Var a2 = true; Var a3 = 1; Var