What exactly is Type Coercion in Javascript?

Question

What exactly is type coercion in Javascript?

For example, on the use of == instead of ===?

Answer 1

What is coercion:

Type coercion in javascript occurs when the Javascript engine has to perform a certain operation for which it needs data to be in a certain type. When the engine encounters data in a certain type that is not applicable for the operation it then coerces the data into a certain type. This is needed because variables in javascript are dynamically typed, which means that a given variable can be assigned a value of any type.

Example:

---

if(1){
  // 1 gets coerced to true
}


if(4 > '3') {
  // 3 gets coerced into a number
}


44 == "44"  // true, the string 44 gets converted to a nr

Boolean coercion:

In javascript coercion, all values are converted to true except for the following values which are coerced to false:

console.log(!!"");         // false
console.log(!!0);          // false
console.log(!!null);       // false
console.log(!!undefined);  // false
console.log(!!NaN);        // false
console.log(!!false);      // false

Also notice that in the above example that the double ! operator is used. The ! mark operator coerces a value into a boolean with the opposite value. We can use this operator twice to convert any value into a boolean.