Implementation Limits

The JavaScript spec does not place arbitrary limits on things such as the number of arguments to a function or the length of a string literal, but these limits exist nonetheless, because of implementation details in different engines.

For example:

function addAll() {
    var sum = 0;
    for (var i=0; i < arguments.length; i++) {
        sum += arguments[i];
    }
    return sum;
}
var nums = [];
for (var i=1; i < 100000; i++) {
    nums.push(i);
}
addAll( 2, 4, 6 );                // 12
addAll.apply( null, nums );        // should be: 499950000

In some JS engines, you’ll get the correct 499950000 answer, but in others (like Safari 6.x), you’ll get the error: “RangeError: Maximum call stack size exceeded.”

Examples of other limits known to exist:

• maximum number of characters allowed in a string literal (not just a string value)
• size (bytes) of data that can be sent in arguments to a function call (aka stack size)
• number of parameters in a function declaration
• maximum depth of non-optimized call stack (i.e., with recursion): how long a chain of function calls from one to the other can be
• number of seconds a JS program can run continuously blocking the browser
• maximum length allowed for a variable name
• …

It’s not very common at all to run into these limits, but you should be aware that limits can and do exist, and importantly that they vary between engines.