Discussion on: Understanding basics of array in javascript

[Frugence Fidel]

In most case let and const are almost same, the only difference I known, const cannot be updated but let can.

Let use this example for demonstration

  const colors = ['purple', 'black', 'yellow', 'aqua'];

 // const

 for(const color of colors) {
    color = 'white';
    console.log(color);  // Uncaught TypeError: Assignment to constant variable.
 }

 // Let

 for(let color of colors) {
    color = 'white';
    console.log(color);  // white white white white
 }

[Olimpio]

Then their aren't same anymore...

[Mehdi Benmessaoud]

Yes i agree with you on that, but i think that’s a miss use of const because inside the loop the variable color is changing at each iteration.

[Frugence Fidel]

When use const in for of loop, in each iteration you get a new variable, which is scoped only to that iteration.

[Frugence Fidel]

I use let only when i want to modify variable's value.

In below example you can't use const because the value of variable is modified by increment one until the condition is false.

  for(let i = 1; i < 3; i++) {
    console.log(i); // 1 and 2
  }

In below example, the constant variable(random) hold each values of that array.

  for(const random of ['a', 'b', 1, 2]  ) {
    // Here it print values that held by constant random without modify it
    console.log(random); // a b 1 2
  }

Remember, to be constant does not mean to hold only single data. const can also hold list of data. Good example is array.

 // Here constant colors is holding two color
 const colors = ['purple', 'black'];

 // First color is purple
 console.log(colors[0]); // 'purple'

 // Second color is black
 console.log(colors[1]); // 'black'