There are several data types in javascript

There are 8 data types in JavaScript, namely number, string, boolean, null, undefined, symbol, bigint and object.

#The operating environment of this article: windows10 system, javascript 1.8.5, thinkpad t480 computer.

First of all, data types in js are divided into primitive data types and reference data types

• Primitive data types

• # #number

• string

• boolean

• null

• undefined

• symbol (ES6)

• bigint (ES10)

• Reference data type

##object
##Include function/array/object
in the reference data type object

let obj = {};
obj.a = 1;
let a = Symbol();
obj[a] = 2; // 此时obj内部的a到底是1还是2呢？我们可以打印一下obj
 
obj {
 a: 1
 Symbol(): 2
 __proto__: Object
} // 此时我们可以发现定义的变量a似乎只是一种标志，并没有具体的属性名

let obj = {};
obj.a = 1;
let a = Symbol('a');
obj[a] = 2; 
 
obj {
 a: 1
 Symbol(a): 2 // 有字符串的Symbol更能区分每个独一无二的标识
 __proto__: Object
}

let a = Number.MAX_SAFE_INTEGER; // 9007199254740991 最大安全整数
console.log(a + 1); // 9007199254740992
console.log(a + 2); // 9007199254740992
console.log(a + 1 === a + 2); // true
// 此时我们可以发现 a + 1 与 a + 2 计算出来的数值是一样的，虽然可以正常计算，但是已经失去了计算的价值

BigInt is a built-in object, which provides a representation that is greater than the maximum safety Methods other than integers, bigint are usually used to calculate values ​​other than the largest safe integer:

BigInt(1) === BigInt('1') === 1n

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