CODEWITHSUNDEEP
javascriptfind
jyoungdev
jyoungdev

Reputation: 2674

How can I find where an object member is defined in Javascript?

Of course, most of the time, I can simply search for the identifier and look at all instances thereof. Often, searching for " =" or " :" will find the answer the fastest.

But this technique fails is situations like this:

// untested javascript:
function AddMemberToObject(object, value, memberName) {
    object[memberName] = value;
}

var myObj = {}

// 3,000 references to myObj

// ... somewhere else
var mysteryString = thisMethodCallsAnotherMethodCallsAnotherMethodEtc();

AddMemberToObject(myObj, someFunction, mysteryString);

// 3,000 more references to myObj

Let's say I haven't discovered the above code yet. As illustrated in this example, some things that make it hard to find where a member is defined include:

What are some techniques for finding where the member is added to the object in difficult cases like this? Is there a way to do this at runtime (e.g. make all additions to an object fire an event, which we can listen for and break on in the debugger)?

Upvotes: 5

Views: 159

Answers (1)

HAL 9000
HAL 9000

Reputation: 3985

Firefox features the non-standard function watch() which watches for a property to be assigned a value and runs a function when that occurs.

Upvotes: 2

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