声明对象文字时出现意外的标识符错误

Question

Trying to complete a simple node.js exercise, I have tried several variations on this. I suspect I am missing something very simple.

The reason I created var Calc was because I wanted to export the 'calculator' function.

the error:

/Users/alex/zdev/react-project/calc.js:4
    var add = function(){
    ^^^

SyntaxError: Unexpected identifier

file calc.js: (file has been shortened to stay concise)

var readline = require('readline-sync');

var Calc = {
        var add = function(){
                var num1 = readline.question("num1: ");
                var num2 = readline.question("num2: ");
                console.log(num1 + num2);
        };
}

module.export = Calc;

calling file:

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

var Calc = new calc.Calc();

Calc.add();
Calc.sub();
Calc.divide();

Answer 1

You define a new object Calc with a function add , but the syntax is incorrect. The correct syntax is:

var Calc = {
  add: function() {
    var num1 = readline.question("num1: ");
    var num2 = readline.question("num2: ");
    console.log(num1 + num2);
  }
};

Answer 2

If you want to make constructor function (I mean from your syntax) you should do it like this:

function Calc() {
}

Calc.prototype.add = function() {
    var num1 = readline.question("num1: ");
    var num2 = readline.question("num2: ");
    console.log(num1 + num2);
};

module.exports = Calc;

and then you import this like:

var Calc = require('./calc');

var calc = new Calc();

calc.add();
calc.sub();
calc.divide();

But I prefer for you to use ES6 class syntax, and the Calc constructor function will look like:

class Calc {
    constructor() {}

    add() {
        var num1 = readline.question("num1: ");
        var num2 = readline.question("num2: ");
        console.log(num1 + num2);
    }
}

module.exports = Calc;

Answer 3

I suggest using JavaScript classes introduced in ECMAScript 2015

class Calculator {
  constructor() {
    console.log("[Calc] created!");
  }

  static add(a, b) {
    return a+b;
  }

}

let Calc = new Calculator();

Answer 4

solution is as follows:

call file:

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

calc file:

var Calc = {
        add: function(){
                var num1 = readline.question("num1: ");
                var num2 = readline.question("num2: ");
                console.log(num1 + num2);
        },
        divide: function(){
                var num1 = readline.question("num1: ");
                var num2 = readline.question("num2: ");
                console.log(num1 / num2);
        },
        sub: function(){
                var num1 = readline.question("num1: ");
                var num2 = readline.question("num2: ");
                console.log(num1 - num2);
        }
}

module.exports = {Calc:Calc}

the following lines pulled are where the original mistakes were:

defining my class after importing from other function

Calc = calc.Calc;

using a commas to seperate my object properties instead of a semicolon

},

not defining a dictionary in module exports. Also, I wrote 'module.export' not 'module.exports' originally

module.exports = {Calc:Calc}

And I forgot to put my parseInt() for my num1 and num2 values.