nodeJS中的重载函数调用

Question

I have two js files add.js and testAdd.js

add.js

module.exports = function add(x,y) {
    console.log("------Starts x+y----");
    var a = x+y;
    console.log(a);
    return a;
}

module.exports = function add(x,y,z) {
    console.log("------Starts x+y+z----");
    var a = x+y+z;
    console.log(a);
    return a;
}

testAdd.js

var add = require('./add');

add(300,100);

add(300,100,233);

From the testAdd I am calling the add method in the add.js

What is happening is function call is always going to the add(x,y,z) as function is not selecting based on the parameters(as in java).

I am new to nodeJS. Can someone help me to understand this flow? And also help me to fix this issue. Thanks in advance.

Attaching the console o/p:-

Answer 1

JavaScript doesn't have function overloading. If you want to have your function take an optional third argument, you can set a default value (with a recent Node version):

function add(x, y, z = 0) {
  ...
}

You can use it with two ( add(300, 100) ) or with three ( add(300, 100, 233) ) arguments.

If you don't have a recent enough Node version, you have to do some manual validation on the third argument:

function add(x, y, z) {
  z = Number.isFinite(z) ? z : 0;
  ...
}

Answer 2

Javascript does not support function overloading. Although robertklep 's solution is great. There is one more way you can use.That is arguments object .

arguments is very good when you have unknown number of parameters to be passed into the function. see more here .

Below is how will it look.

//add.js
function add() {
  var args=Array.prototype.slice.call(arguments);
  console.log(arguments);
  console.log(args);
  console.log("------Starts x+y+z+.....and so on----");
  var ans = args.reduce(function(prev,curr){return prev+curr;});
  console.log(ans);
  return ans;
}
var sum = add(1,8,32,4);
module.exports = add;//to make it available outside.

On executing the above.(as node add.js ),The output is as follows.

{ '0': 1, '1': 8, '2': 32, '3': 4 }
[ 1, 8, 32, 4 ]
------Starts x+y+z+.....and so on----
45