How Can JavaScript Function Name Collisions with Element IDs Be Avoided?

Function Name Collisions with Element ID in JavaScript

Web developers often encounter a peculiar issue where a JavaScript function name conflicts with an element ID, leading to errors such as "is not a function." This issue stems from a legacy feature of JavaScript that originated in the early days of web development.

Legacy Scope Chain Issue

In JavaScript 1.0 to 1.3, there was no clear distinction between the programming language and the DOM API. Consequently, form controls have access to the form object's properties, including the names of the controls. This means that if a select element has an ID of "border," the following code will work:

function border(border) { alert(border); }
<select>

However, this simplicity comes with a caveat. If a form control is placed within a form, the form object becomes third-next in the scope chain. As a result, the following code will fail:

<form>
  <select>

In this case, the "border" property of the form object overshadows the global "border" function, causing the "is not a function" error.

W3C DOM Level 2 HTML Compatibility

To address this issue, W3C DOM Level 2 HTML introduced the ability to access elements by their names or IDs via the bracket property accessor syntax. This means that the following code is now equivalent to the problematic code above:

document.forms["myForm"].elements["border"](this.value)

Recommendation

To avoid this collision issue, it is advisable to avoid using the same name or ID for form controls as for user-defined functions. Additionally, developers should steer clear of using the same identifier for the function and one of its arguments, as it renders the function object inaccessible from within the function.

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