JavaScript original value and object reference instance analysis_javascript skills

The examples in this article describe the methods of JavaScript primitive values ​​and object references. Share it with everyone for your reference. The specific analysis is as follows:

In one sentence: primitive values ​​are immutable, while object references are mutable.

Primitive values ​​(undefined, null, Boolean values, numbers and strings) in js are essentially different from objects (including arrays and functions). The original value cannot be changed, and no method can change an original value; for strings, all methods in the string appear to return a modified string, but actually return a new string value. :

var str="hello world";
s.toUpperCase();
s;     //仍然不变

Comparison of primitive values ​​is a comparison of values: they only wait if their values ​​are equal.

Objects are different from primitive values. First of all, they are mutable; secondly, the comparison of objects is not the comparison of values; the comparison of objects is the comparison of references: they only want to wait if and only if they refer to the same basic object. .
If you want to compare two separate objects or arrays, you must compare their properties or elements, as follows:

function equ_arrays(a,b){
  if(a.length != b.lenght) return false;
  for(var i=0;i<a.length;i++)
    if(a[i] !== b[i]) return false;
  return true;
}

I hope this article will be helpful to everyone’s JavaScript programming design.