assignByValue.js

// This work with assigning by value
var i = 3
// 3
j = i
// 3
j += 1
// 4
i
// 3
j
// 4

// This work with assigning by reference
var i = [1,2,3]
i // (3) [1,2,3]
j = i
// (3) [1,2,3]
j.push(4)
// 4
j // (4) [1,2,3,4]
i // (4) [1,2,3,4]

// This make assign only value, rather than assign reference
var i = [1,2,3]
var j = [...i]
j.push(4)
// 4
i
// (3) [1,2,3]
j
// (4) [1,2,3,4]