jQuery .prop() vs. .attr(): When Should I Use Each Method?

jQuery .prop() vs .attr()

jQuery 1.6 introduced the new prop() method, which raised some questions about its usage compared to the existing attr() method.

When to Use .prop()

In general, you should prefer prop() over attr() for the following reasons:

• Accuracy: prop() retrieves the actual property of the DOM element, while attr() retrieves the attribute, which may not always reflect the current state of the element.
• Type awareness: prop() returns the property value in its correct type (e.g., a Boolean for checked), while attr() always returns a string.
• Clarity: prop() is more explicit about which property you're accessing.

When to Use .attr()

attr() is still useful in certain situations:

• Custom attributes: attr() can retrieve or set custom attributes that you add to the DOM.
• Boolean attributes: For some Boolean attributes (e.g., checked), prop() will reflect the current state, while attr() will reflect the default value (although jQuery 1.6.1 reverted attr() to its old behavior for Boolean attributes).

Differences in Attribute and Property Behavior

The main difference between attributes and properties is that attributes are stored in the HTML markup, while properties are dynamically computed by the browser. This can lead to discrepancies in certain cases, such as:

• Input value and checked state: The value and checked properties represent the current state of the input element, while the corresponding attributes (value and checked) represent the default or initial state.
• Style: The style property is an object that contains CSS properties, while the style attribute is a string representation of the inline CSS.

Impact on Existing Code

Replacing all instances of attr() with prop() in jQuery 1.6 will generally work. However, you may need to manually handle Boolean attributes where you previously relied on attr() to reflect the default state.

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