Post by account_disabled on Dec 25, 2023 22:30:00 GMT -6
Chrome DevTools allows you to identify the portions of the page that are painted Chrome DevTools allows you to identify the portions of the page that are painted Optimizing the paint process may not be that easy, and you should use your browser's development tools to measure the time the browser takes to fire each paint event. You can read more about this topic in Google's Rendering Performance guide . Prevent Rendering-Blocking JavaScript When the browser encounters a script tag, it must stop parsing the HTML code. Inline scripts execute exactly where they are in the document and block the construction of the DOM until the JS engine finishes its execution. In other words, inline JavaScript can significantly delay the initial rendering of the page.
But JavaScript also allows you to manipulate CSS properties, so the browser must Country Email List pause execution of the script until it has finished downloading and building the CSSOM. This means that JavaScript causes parsing to block . In the case of external JS files, the parser must also wait until the resource has been retrieved from the cache or remote server, and this could severely slow down the time it takes to first render the page. That said, what can we do to minimize the time it takes the browser to load and execute JavaScript? Load JavaScript asynchronously : The asynctag's Boolean attribute scriptinstructs the browser to execute the script asynchronously, if possible, without blocking the construction of the DOM.
The browser sends the HTTP request for the script and continues parsing the DOM. Furthermore, the script does not block the construction of the CSSOM, which means it will not block the Critical Rendering Path (see the MDN documentation for more information on script tag attributes ) Defer JavaScriptdefer : The tag's Boolean attribute scripttells the browser to execute the script after parsing the document, but before firing the event DOMContentLoaded. This attribute should not be used if the src attribute is absent, i.e. in inline scripts (to learn more, read Mozilla Hacks ) Defer JavaScript code inline : Many scripts don't manipulate the DOM or CSSOM, so there's no reason to block parsing . Unfortunately, we can't use asynce attributes deferfor inline scripts, so the only way to load them after the document has loaded is to move them down. The advantage is that inline scripts do not require additional HTTP requests.
But JavaScript also allows you to manipulate CSS properties, so the browser must Country Email List pause execution of the script until it has finished downloading and building the CSSOM. This means that JavaScript causes parsing to block . In the case of external JS files, the parser must also wait until the resource has been retrieved from the cache or remote server, and this could severely slow down the time it takes to first render the page. That said, what can we do to minimize the time it takes the browser to load and execute JavaScript? Load JavaScript asynchronously : The asynctag's Boolean attribute scriptinstructs the browser to execute the script asynchronously, if possible, without blocking the construction of the DOM.
The browser sends the HTTP request for the script and continues parsing the DOM. Furthermore, the script does not block the construction of the CSSOM, which means it will not block the Critical Rendering Path (see the MDN documentation for more information on script tag attributes ) Defer JavaScriptdefer : The tag's Boolean attribute scripttells the browser to execute the script after parsing the document, but before firing the event DOMContentLoaded. This attribute should not be used if the src attribute is absent, i.e. in inline scripts (to learn more, read Mozilla Hacks ) Defer JavaScript code inline : Many scripts don't manipulate the DOM or CSSOM, so there's no reason to block parsing . Unfortunately, we can't use asynce attributes deferfor inline scripts, so the only way to load them after the document has loaded is to move them down. The advantage is that inline scripts do not require additional HTTP requests.