Javascript value types and reference types

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JavaScript variable type

1. Value types: String, Number, Boolean, Null, Undefined

2. Reference types: Arrays, objects, functions

Comparison of value types and reference types

Compare these two types with two instances (Debug environment: Chrome Developer Tools Console)

Value type instance

var a = ‘hello‘;var b = a;b;          /* hello */a = ‘world‘;b;          /* hello */

The value type of the variable assignment process, is actually allocated a new memory space, the same value but the two do not interfere

Reference type instance

/* 对象或数组 */var a = {"x": 0};var b = a;b.x;            /* 0 */a.x = 1;b.x;            /* 1 */a = {"x": 2};   /* 此时，a 指向了另一块内存空间，b 的值将不受干扰 */b.x;            /* 1 */a.x = 3;b.x;            /* 1 *//* 函数 */var a = new Function("alert(‘test‘)");var b = a;b();            /* 执行 alert(‘test‘) */

The variable assignment procedure for a reference type refers to two variables pointing to the same piece of memory space, where a change in the value of one variable causes a change in the value of the other variable

Javascript value types and reference types