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up vote 0 down vote favorite

Take an object like this

book.chapter.paragraph.sentence.word

assume you want to retrieve a certain word

book[6][3][15][3]

to be certain to reference an existing word, do you really have to perform a check like this...

if(typeof book[6] !== "undefined" && typeof book[6][3] !== "undefined" && typeof book [6][3][15] !== "undefined" && typeof book[6][3][15][3] !== "undefined") ...

...or is there a better way?

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up vote 0 down vote

Normally for dynamic access to nested properties you are expected to make an iterative check. However you might also use a try catch and parse the error message ugliness to access the undefined property. Such as 

try{
var book = {page111: {paragraph2:{sentence4:{word12:"test"}}}};
    list = ["page112","paragraph2","sentence4","word12"],
    word = book[list[0]][list[1]][list[2]][list[3]];
    console.log(word);
}catch(e){console.log(list[list.indexOf(e.message.match(/\'(.*)\'/)[1])-1], "is undefined")}

I have to agree that it is very ugly.

share|improve this answer
    
You say that an iterative check is expected: this was, in fact, my first idea. I thought it would be an atrocious solution, but if it is the norm as you imply, I would go for that. I assumed there could be a built-in function for this kind of iterative check, that I was somehow missing... – resle 14 hours ago

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