Chrome DevTools code snippets

Performance, debugging and testing code snippets to be run in Chrome DevTools

Read Code Snippets tutorial, Performance profiling using DevTools code snippets and How to improve Angular application performance using code snippets.

Snippets

DOM and CPU generic performance

boilerplate.js - boilerplate for loading and running a remote code script (see remote download).
first-paint.js - time from page reload to first visible contents.
timing.js - Detailed page timing information, from addyosmani/timing.js.
time-method-call.js - measures single method call time.
profile-method-call.js - profiles a single method call.

Storage measurements

local-storage-size.js - measures size of the strings in the localStorage.
expensive-keys.js - measures how much space individual keys and their values take up in a collection of objects, read Measuring Space Allocation.
keys-vs-values.js - measures length of keys vs length of values in an array.

Angular performance

ng-count-watchers.js - counts total watchers in the page. More watchers - slower digest cycle.
ng-idle-apply-timing.js - measures how long a digest cycle takes without any data changes. This measures purely how long all watched expressions take to compute and compare to previous values (dirty checking).
ng-profile-scope-method.js - installs profile calls around a given scope method. When the method completes, the original non-instrumented version will be restored. The browser will have timeline and CPU profile.
ng-run-digest-cycle.js - triggers digest cycle starting with root scope.
ng-profile-data-change.js - changes data on the scope, runs digest cycle to profile listeners.
ng-scope-size.js - finds total size of all user objects attached to all scopes. Smaller data - faster copying and comparison during digest cycle.
ng-find-scope-property.js - finds all scopes that own a property with given name.
ng-profile-local-digest.js - runs idle digest cycle starting at the scope that surrounds given selector. Useful to find parts of the page with expensive watchers.
ng-find-expensive-digest.js builds upon ng-profile-local-digest.js to measure digest duration for several selectors and print sorted table starting with the slowest digest duration.

All snippets, including mine are distributed under MIT license.

Remote download

You can download and run a snippet by using the following boilerplate (scripts are via downloaded via RawGit)

(function firstPaintRemote() {
  // form rawGit proxy url
  var ghUrl = 'bahmutov/code-snippets/master/first-paint.js';
  var rawUrl = 'https://rawgit.com/' + ghUrl;
  // download and run the script
  var head = document.getElementsByTagName('head')[0];
  var script = document.createElement('script');
  script.type = 'text/javascript';
  script.src = rawUrl;
  head.appendChild(script);
}());

Small print

License: MIT - do anything with the code, but don't blame me if it does not work.

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Support: if you find any problems with this module, email / tweet / open issue on Github