Why Do JavaScript Function Names Sometimes Conflict with Element IDs?

Why JavaScript Function Name Conflicts with Element ID: An In-Depth Exploration

In the realm of JavaScript development, a perplexing issue arises when function names clash with element IDs. This query delves into the underlying reasons and explores the restrictions and implications of such conflicts.

Understanding the Conflict

Consider the following example:

<script>
    function border(border) { alert(border); }
</script>

<select>

In the first fiddle, this code successfully alerts the selected option's value. However, in the second fiddle, using a form element (with a form surrounding the select), the code fails with the error "border is not a function."

This discrepancy stems from a legacy issue in JavaScript, where the scope chain of event-handler attribute values includes the enclosing Form object. This Form object possesses properties representing the names of its child controls, including the border select element.

Thus, when referring to border as the function in the event handler within the form context:

<form><… name="border" onchange='border(this.value)' …></form>

This is equivalent to calling form.border(this.value), which references the Form object's property instead of the intended function.

JavaScript Specifications and Restrictions

The JavaScript language specification does not explicitly forbid naming conflicts between functions and element IDs. However, the DOM Level 2 HTML Binding specifies that HTMLCollections (including forms and their controls) can be accessed by name or ID using bracket syntax.

This implies that:

• Element IDs can act as property names for their parent forms,
• Form property names can conflict with functions with the same name.

Consequences of Conflicts

Using the same identifier for both an element and a function can:

• Cause function invocation errors: When a script tries to call the function, it may instead access the element object, resulting in an exception.
• Shadow function objects: The function becomes inaccessible from within the function itself, as the Variable Object resides atop its scope chain.

Avoiding Conflicts

To avoid these issues, consider following these guidelines:

• Use distinct names for functions and element IDs.
• Avoid using reserved form property names (e.g., "action", "submit", "reset") for functions.
• Be aware that using the same identifier for both the function and one of its arguments may render the function недоступный.

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