Explanation of basic syntax and variables of JavaScript

Technical answers to the basic syntax of JavaScript and variables

1. Grammar

• JavaScript is size-sensitive written.

• Identifier refers to the name of a variable, function or attribute, or the parameter of a function. The following rules must be met:

            第一个字符必须是一个字母，下划线（_）或者一个美元符号（$）;
  
            其他字符可以是字母、下划线、美元符号、数字；
  
            按照惯例，采用驼峰命名的方式，就是第一个字母小写，剩下的每个有意义的单词首字母大写；
  
            不能把关键字、保留字、true、false、和null用作标识符；

  Copy after login

• Comments

 //用双斜杠可以注释单行。

  /*
  *
 * 用斜杠、若干星号、斜杠以这种形式注释多行。 
 * 
  */

• The statement ends with a semicolon.

  Adding a semicolon can avoid unnecessary trouble. In other words, adding a semicolon is not a rigid rule. When adding a semicolon to compress the code later, it improves the performance of the code because it does not require the system to Analyze where it ends and begins.

• Use a code block, which can start with a left curly brace ({) and end with a right curly brace (}).

  2. Variables

• ECMAScript variables are loosely typed, which means they can save any type of data.

• Supports initializing variables. Assigning values ​​to undeclared variables in strict mode will throw a ReferenceError.

• You can use one statement to define multiple variables, separated by commas, as in the following example:

var message="hi",
    found=false,
    lost=true,
    number=20;

The above is me I compiled it for everyone, I hope it will be helpful to everyone in the future.

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