Question

I would like to call some functions by shorter alias in order to minimize code size.

(function(){
    var t = document.getElementById;
    t('element-id');
})();

This piece of code gives Error: Could not convert JavaScript argument. Why?

Answer 1

When you assign a function to a different variable, it’s this value changes. Since getElementById expects this to be an element, you’re getting an error.

If you’re in an environment where you can use bind, use it:

(function(){
    var t = document.getElementById.bind(document);
    t('element-id');
})();

This’ll ensure that t‘s this will stay the document object.

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If you can’t use bind, you’ll have to create an intermediary function:

(function() {
    function t (id) {
        document.getElementById(id);
    }
    t('element-id');
})();