JS Input/Output Solution 4

What will happen, if we declare an array using a const and try to change one of its values?

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const s = [5, 6, 7];
s[2] = 45;
console.log(s);    // ?

Solution

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const s = [5, 6, 7];
s[2] = 45;
console.log(s);    // [5, 6, 45]

You might think that value will not get modified here and we will receive an error: “TypeError: Assignment to constant variable.”

But, instead our array value gets modified and prints a the modified array.

This is because, constprevents the reference of a variable from getting changed, but in the case of an array or an object the reference remains same and only the property is getting modified.

If you try to change the reference and point the variable to an entirely new object or array, then you will get an error.

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const s = [5, 6, 7];
s = [5, 6, 45]
console.log(s);    // TypeError: Assignment to constant variable

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