javascript set variable to null

1) Intro Not long ago I set up a technology group in a MM asked a question like this, she posted the code as follows: var a = 1;function hehe (){Window.alert (a);var a = 2;Window.alert (a);}Hehe (); The results of the execution are as follows:

When a field in the database is set to Null, the mobile phone will return Null by default. if I want the mobile phone to return Null, I have to make a judgment. 1. if I want to leave the returned result blank on the mobile phone, I will not make any

JavaScript Learning record day6-function variable scope, deconstruction assignment and method@ (learning) [JavaScript][TOC]1. ScopeIn JavaScript, variables that are var declared are actually scoped.If a variable is declared inside the function body,

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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

Most computer languages have and have only one value that denotes "none", such as the nil of the None,ruby language of the Null,python language of the C language Null,java language. Oddly enough, the JavaScript language actually has two values that

Front. The General program language, which indicates null only NULL, but JavaScript designer Brendan Eich but designed a undefined, which undoubtedly increased the complexity of the program, but there are some reasons for this. This article

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

, native JavaScript implements string length interceptionView Code2. Native JavaScript gets the domain hostView Code3. Native JavaScript Clear spaceView Code4. Native JavaScript replaces allView Code5. Native JavaScript Escape HTML tagView Code6.

Variable scope is a topic involved in every programming language. It is also a required knowledge point for a programmer. It is helpful for you to deeply understand the variable scope and write stable programs. JavaScript itself, as a simple