Why is there an error on this line of Javascript code?

Question

There is a code that on this line of code

 Boo.prototype.initone (a) { <-- Syntax error

I want to create a simple object of Boo with one property this.bar why would this be giving me an error? The error is listed below which is an uncaught Syntax Error but I am not seeing it.

I know that syntax errors should not be posted but I am just not seeing what is completely wrong with this code below.

Error Code Here:

 Boo.prototype.initone (a) {
     this.bar = a;
     return this;
 }

Error

 Uncaught SyntaxError: Unexpected token {

Code:

<script>
function Test1() {
}

function Boo () {
    this.bar = 'Test This Method';
}

Boo.prototype.initone (a) {
    this.bar = a;
    return this;
}

Boo.prototype.inittwo (b) {
    this.bar = 'something to do with ' + b;
    return this;
}

var a = new Boo().initone('constructor 1');
var b = new Boo().inittwo('constructor 2');
</script>

Code: This code will still show an uncaught exception. If I take the return this out then no error will occur on initone but inittwo seems to be ok.

Boo.prototype.initone = function (a) {
    this.bar = a;
    return this;
}

Boo.prototype.inittwo = function (b) {
    this.bar = 'something to do with ' + b;
    return this;
}

What made you think that Boo.prototype.initone (a) { } would define a function? — Felix Kling
– Felix Kling, Commented Jul 7, 2014 at 2:25
Your updated code will not throw a SyntaxError. If it does, then there's some other problem outside that code. Or is it a different error? If you're in strict mode, it's possible for the value of this to be null or undefined, which would result in a TypeError. — cookie monster
– cookie monster, Commented Jul 7, 2014 at 3:22
The code in your question runs with no exceptions (fiddle). If you're still getting errors, we need to see more of the code. — Sean Walsh
– Sean Walsh, Commented Jul 7, 2014 at 4:46

Sean Walsh · Accepted Answer · 2014-07-07 02:23:22Z

5

You're getting a syntax error here because JavaScript doesn't know what you want to do. If you're defining a function, you need to specify it with the function keyword.

In this case, it needs to be written as:

Boo.prototype.initone = function(a) {
    this.bar = a;
    return this;
}

You'll also need to make the change on your inittwo method.

answered Jul 7, 2014 at 2:23

Sean Walsh

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Comments

mtyson · Accepted Answer · 2014-07-07 02:27:24Z

3

Because that's not how you define a function on an object in JS :)

You have to use an equals sign:

Foo.prototype.initone = function(bar){
}

I think you are remembering the syntax for defining a function like so:

function f() { }

answered Jul 7, 2014 at 2:27

mtyson

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