A brief analysis of JS original value and reference value issues

Primitive values -> primitive types

Number String Boolean undefined null

Simple data segments stored on the stack, that is, their values are stored directly at the location where the variable is accessed

Dynamic language -> scripting language -> interpreted language -> weakly typed language

Static language -> compiled language -> strongly typed language

null empty value initialization component function destruction function placeholder

Reference Value

object array function date RegExp

If a value is of a reference type, its storage is allocated from the heap. Since the size of the reference value will change, it cannot be placed on the stack, otherwise it will slow down the variable search. Instead, the value placed in the variable's stack space is the address where the object is stored on the heap. The address size is fixed, so storing it on the stack has no negative impact on the variable's performance.
ex

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>D1</title>
</head>
<body>
    <script type="text/javascript">
        var arr1 = [1,2,3,4];
        var arr2 = arr1;
        //arr1.push(5); //At this time, arr2 is printed as 1, 2, 3, 4, 5
        arr1 = [1,2]; //Reassigning value will not affect arr2
        document.write(arr2);
    </script>
</body>
</html>

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