window.location.assign(url) vs window.open(url, '_self'): Key Differences Explained in JavaScript

Table of Contents#

1. What is window.location.assign(url)?
2. What is window.open(url, '_self')?
3. Key Differences: A Detailed Comparison
   • Primary Purpose
   • Syntax and Parameters
   • History Management
   • Return Value
   • Security and Pop-up Blockers
   • Browser Compatibility
4. When to Use Each Method
5. Common Pitfalls to Avoid
6. Conclusion
7. References

What is window.location.assign(url)?#

The window.location.assign(url) method is part of the Location interface, which provides information about the current URL and allows navigation to a new URL. As the name suggests, its sole purpose is to navigate the current browsing context (window or frame) to a specified URL.

How It Works:#

When called, assign(url) loads the resource at url in the current window. It adds a new entry to the browser’s session history, meaning the user can click the "Back" button to return to the previous page.

Syntax:#

window.location.assign(url);

• Parameter: url (string) – The URL to navigate to (e.g., "https://example.com").

Example:#

// Navigate to "https://example.com" when a button is clicked
document.getElementById("navigate-btn").addEventListener("click", () => {
  window.location.assign("https://example.com");
});

Key Characteristics:#

• Explicitly designed for navigation in the current window.
• Modifies the session history by adding a new entry.
• No return value (returns undefined).

What is window.open(url, '_self')?#

window.open(url, target, features) is a more versatile method that opens a new browser window or tab by default. However, when the target parameter is set to '_self', it loads the URL in the current browsing context (the same window or frame), mimicking navigation behavior.

How It Works:#

The window.open() method’s behavior depends heavily on the target parameter:

• '_blank': Opens in a new tab/window (default).
• '_self': Opens in the current window/frame.
• '_parent'/'_top': Opens in the parent frame or top-level window (for framesets).

When target: '_self', window.open(url, '_self') navigates the current window to url, similar to location.assign().

Syntax:#

window.open(url, target, [features]);

• Parameters:
  • url (string): The URL to load (required).
  • target (string): The browsing context to load the URL in (e.g., '_self', '_blank').
  • features (string, optional): Comma-separated list of window features (e.g., width=500,height=600); ignored for '_self'.

Example:#

// Navigate to "https://example.com" in the current window
document.getElementById("open-self-btn").addEventListener("click", () => {
  window.open("https://example.com", "_self");
});

Key Characteristics:#

• Originally designed to open new windows/tabs, but can force current-window navigation with '_self'.
• Behavior depends on the target parameter (flexible but less explicit for current-window navigation).

Key Differences: A Detailed Comparison#

While location.assign(url) and window.open(url, '_self') can both navigate the current window, their underlying design and behavior differ in critical ways. Here’s a breakdown:

1. Primary Purpose#

2. Syntax and Parameters#

3. History Management#

Both methods add a new entry to the session history (so the user can click "Back" to return to the previous page). For example:

• If you’re on Page A and call assign("PageB") or open("PageB", "_self"), Page B loads, and the history stack becomes [Page A, Page B].
• Clicking "Back" returns to Page A.

Note: This differs from window.location.replace(url), which replaces the current history entry (no "Back" to the original page).

4. Return Value#

Example:

const result1 = window.location.assign("https://example.com");
console.log(result1); // undefined
 
const result2 = window.open("https://example.com", "_self");
console.log(result2); // null (no new window)

5. Security and Pop-up Blockers#

6. Flexibility#

Summary Table#

When to Use Each Method#

Use window.location.assign(url) When:#

• You need to explicitly navigate the current window (most common use case).
• Readability and intent matter (code clearly signals "navigate here").
• You want to avoid unnecessary complexity (no extra parameters).

Use window.open(url, '_self') When:#

• You’re already using window.open() for other targets (e.g., '_blank' for new tabs) and want consistency in code style.
• You need to dynamically switch targets (e.g., toggle between '_self' and '_blank' based on user settings).

Note: In most cases, assign(url) is preferred for current-window navigation due to its clarity and simplicity.

Common Pitfalls to Avoid#

1. Confusing open('_self') with location.replace(url):
   Neither method replaces the current history entry. Use window.location.replace(url) if you want to prevent the user from returning to the previous page.

2. Overusing window.open() for current navigation:
   Using open(url, '_self') when assign(url) would suffice makes code less readable and risks accidental use of other targets (e.g., '_blank'), triggering pop-up blockers.

3. Ignoring return values:
   Assuming window.open(url, '_self') returns a Window object (it returns null), leading to errors when trying to interact with the "new window."

Conclusion#

window.location.assign(url) and window.open(url, '_self') both navigate the current window, but they serve different primary purposes. assign(url) is explicitly designed for current-window navigation, offering clarity and simplicity. window.open(url, '_self'), while functional, is a side effect of a method built for opening new windows/tabs.

For most use cases, window.location.assign(url) is the better choice for current-window navigation: it’s readable, intent-driven, and avoids unnecessary complexity. Reserve window.open() for scenarios where you need to open new tabs/windows, and use '_self' sparingly only for consistency with existing open() logic.

References#

• MDN Web Docs: window.location.assign()
• MDN Web Docs: window.open()
• MDN Web Docs: Location Interface