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Sep 15, 2008 · 2. To open the dedicated ‘Console’ panel, either: Use the keyboard shortcuts. On Windows and Linux: Ctrl + Shift + J. On Mac: Cmd + Option + J. Select the Chrome Menu icon, menu -> More Tools -> JavaScript Console. Or if the Chrome Developer Tools are already open, press the ‘Console’ tab. Please refer here.
- Reproduce The Bug
- Get Familiar with The Sources Panel UI
- Pause The Code with A Breakpoint
- Step Through The Code
- Set A Line-Of-Code Breakpoint
- Check Variable Values
- Apply A Fix
- Next Steps
Finding a series of actions that consistently reproduces a bug is always the first step todebugging. 1. Open this demoin a new tab. 2. Enter 5 in the Number 1box. 3. Enter 1 in the Number 2box. 4. Click Add Number 1 and Number 2. The label below the button says 5 + 1 = 51. The resultshould be 6. This is the bug you're going to fix. In this example,...
DevTools provides a lot of different tools for different tasks, such as changing CSS, profiling pageload performance, and monitoring network requests. The Sourcespanel is where you debugJavaScript. 1. Open DevTools and navigate to the Sourcespanel. The Sourcespanel has three sections: 1. The Pagetab with the file tree. Every file that the page requ...
A common method for debugging a problem like this is to insert a lot of console.log()statementsinto the code, in order to inspect values as the script executes. For example: The console.log() method may get the job done, but breakpoints can get it done faster. Abreakpoint lets you pause your code in the middle of its execution, and examine all valu...
One common cause of bugs is when a script executes in the wrong order. Stepping through your codelets you walk through your code's execution, one line at a time, and figure out exactly whereit's executing in a different order than you expected. Try it now: 1. On the Sources panel of DevTools, click step_into Step into next function call to step thr...
Line-of-code breakpoints are the most common type of breakpoint. When you've got a specific line ofcode that you want to pause on, use a line-of-code breakpoint: 1. Look at the last line of code in updateLabel():label.textContent=addend1+' +' +addend2+' =' +sum; 2. To the left of the code you can see the line number of this particular line of code,...
The values of addend1, addend2, and sumlook suspicious. They're wrapped in quotes, whichmeans that they're strings. This is a good hypothesis for the explaining the cause of the bug. Nowit's time to gather more information. DevTools provides a lot of tools for examining variablevalues.
You've found a fix for the bug. All that's left is to try out your fix by editing the code andre-running the demo. You don't need to leave DevTools to apply the fix. You can edit JavaScript codedirectly within the DevTools UI. Try it now: 1. Click resume Resume script execution. 2. In the Code Editor, replace line 31, var sum = addend1 + addend2, w...
This tutorial only showed you two ways to set breakpoints. DevTools offers many other ways,including: 1. Conditional breakpoints that are only triggered when the condition that you provide is true. 2. Breakpoints on caught or uncaught exceptions. 3. XHR breakpoints that are triggered when the requested URL matches a substring that you provide. See ...
Apr 18, 2018 · This interactive tutorial shows you how to run JavaScript in the Chrome DevTools Console. See Get Started With Logging Messages to learn how to log messages to the Console. See Get Started With Debugging JavaScript to learn how to pause JavaScript code and step through it one line at a time. Figure 1. The Console. Overview
May 9, 2020 · Start by navigating to the project directory and into the part-8 directory: cd Design-and-Build-a-Chat-Application-with-Socket.io. cd part-8. Next, install the npm packages for the project: npm install. Then, start the server: npm start. If you visit 127.0.0.1:3000 in Chrome, you should see a prompt for username.
Aug 7, 2022 · To do this: Open Chrome DevTools and go to the Sources panel. Navigate to the file navigator pane and select main.js to open its content in the code editor. Within the code editor, click at line number 21, right on the number digit, not on the code.
Jan 4, 2017 · To edit a script: Open the file in the Editor pane of the Sources panel. Make your changes in the Editor pane. Press Command + S (Mac) or Ctrl + S (Windows, Linux) to save. DevTools patches the entire JS file into Chrome's JavaScript engine. The Editor pane on the screenshot above is outlined in blue.
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Jun 26, 2022 · Open the example page in Chrome. Turn on developer tools with F12 (Mac: Cmd + Opt + I). Select the Sources panel. Here’s what you should see if you are doing it for the first time: The toggler button opens the tab with files. Let’s click it and select hello.js in the tree view. Here’s what should show up:
