In ES6, we can put the default values right in the signature of the functions.
Default parameters allow you to define a parameter in advance, which can be helpful in certain scenarios.
In ES5, we had to use the below approach.
function add(num1, num2) {
return num1+num2;
}
add (2,3); // Output : 5
add(5); // Output : NaN as num2 is undefined
In ES6, we had to use the below approach.
function add(num1=5, num2=10) {
return num1+num2;
}
console.log (add (2,3)); // Output : 5
console.log (add (7)); // Output : 17
console.log(add()); // Output : 15
add (2,3) - When both argument are passed, num1 takes 2 & num2 takes 3.
add(7) - When one argument is passed, num1 takes 7 & num2 takes default value which is 10.
add( ) - When no argument is passed, num1 & num2 takes default value which is 5 & 10 respectively.
Using Expressions as Default Values
It is also possible to provide expressions as default values.
Example 1: Passing Parameter as Default Values
function multy(x=2, y=x, z=x * y) {
console.log(x * y *z);
}
multy(); // Output:16
Example 2: Passing Function Value as Default Value
const multy = () => 10;
const calculate= function(x,y=x * multy()){
return x+y;
}
const result =calculate(10);
console.log(result); // Output : 110
