Set default parameter values for JavaScript functions

You can add different default values to your JavaScript functions with a simple trick. Let’s see how it works.

Default value for JS function parameters is undefined if you don’t explicitly pass the value when you call the function.

function log(value) {
  console.log(value);
}

log(123); // 123
log();    // undefined

So, the function log prints its argument to the console and if you don’t pass the argument the output is undefined.

Let’s add a default parameter value hello that will be used if the function log is called without arguments.

function log(value = 'hello') {
  console.log(value);
}

log(123); // 123
log();    // hello