JavaScript has several constants

JavaScript has 5 types of constants, which are: 1. Integer constants, which are actually positive numbers; 2. Real constants, which are actually decimals; 3. String constants, which are actually using single or double quotes. The enclosed content; 4. Boolean constant; 5. Custom constant, defined using the statement "const constant name = constant value;".

The operating environment of this tutorial: windows7 system, javascript version 1.8.5, Dell G3 computer.

What are constants

• Constants represent some fixed data

• In real life Human gender can actually be regarded as constants. If you are born a boy, you will be a boy throughout your life. If you are born a girl, you will be a girl throughout your life.

Classification of constants in JavaScript

• Integer constants
  • Integer constants are actually positive numbers. Any integer written in JavaScript is an integer constant
  • 1 / 666 / 99
• Real constants
  • Real constants are actually decimal, which can be used casually in JavaScript Writing a decimal is a real constant
  • 3.14 / 6.66
• String constant
  • String constant is actually used Single quotation marks or double quotation marksenclose the content, we call it a string constant
  • 'a'
  • 'abc'
  • “1”
  • “BNTang”
  • Note: No matter how many characters are enclosed in single quotes or double quotes, in JavaScript String constant
• Boolean constant
  Boolean constant is actually
  • true or false, in In JavaScript, true and false are used to express
  In JavaScript, Boolean constants have only two values, true (true) or false (false)
• Custom constants
  Newly added in
  • ES6
  • const constant name = constant take Value;

const NUM = 666;

// NUM = 888; //尝试修改NUM这个常量的取值，会发现报错了，常量一旦定义就不能再去改变值了

console.log(NUM);

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