General question about Objects

Question

This is not part of any Treehouse course (it's from the "You Don't Know JS" book series), but I'd really appreciate your help:

In the following code:

var obj = {
    a: "hello world",
    b: 42
};

var b = "a";

obj[b];         // "hello world"
obj["b"];       // 42

... how come obj[b] returns "hello world" ? I really don't understand it....

Thanks in advance.

Answer 1 · 2017-10-30T19:41:23Z

October 30, 2017 7:41pm

Since b is a string variable that contains the letter "a", the expression obj[b] is the same thing as obj["a"] which is also the same thing as obj.a.

All of them access the "a" property of obj, which contains "hello world".

This is a good illustration of how variable name choice can influence how easy a program is to understand and maintain. For example, it might have been much less confusing if the variable b had been given the name prop instead.

Answer 2 · 2017-10-31T11:57:24Z

October 31, 2017 11:57am

Thanks a lot for this, Steven. Now it's clearer. But... isn't this a glitch or bug, technically?

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Xavi Guasch

Xavi Guasch

General question about Objects

2 Answers

Steven Parker

Steven Parker

Xavi Guasch

Xavi Guasch

Steven Parker

Steven Parker