passive.js

// declaring an independent variable
let a = 50
// declaring a mathematical constraint between the variable a and b
let b = a + 100
// variable b is now holding value 150
console.log(b) // 150
// manipulating value of variable a
a = 100
// variable b is still holding value 150
console.log(b) // 150
// unless we reassign the constraint between variable a and b,
// we can't have the contraint hold true.
b = a + 100
// variable b is now holding value 200
console.log(b) // 200