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Nadia Stoffel
2,964 PointsWhat's the difference between assigning express() the function and express the variable to var app?
'use strict';
var express = require('express');
var app = express();
I would have thought the 3rd line would be var app = express;
since it was declared as a variable (object) above.
Can someone clear this up?
2 Answers
Steven Parker
243,656 PointsIn JavaScript, functions are "first class objects".
This means that functions can be assigned to variables, passed as parameters, and also returned as values.
So if a function (like "require") returns another function when you call it, then when you assign that to a variable (like "express" in your example) that variable can be used to invoke the returned function.
So the line var app = express(); first invokes the function in express, then assigns the result of calling that function to the variable "app". Without the parentheses, "app" would become a copy of the express function.
Make sense now? I also found this neat article that goes into more depth and with several examples.
noamalffasy
22,398 PointsThat's because you're calling the function express(). Also mentioned here.