USE F12 DEBUGGER CODE THAT HANDLES

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Use F12 Debugger Code That Handles

How to make iterator usable inside async callback functionAs you work with the F12 debugger, you will notice a few things. On the HTML code panel, when you right-click on the desired element, you can select the conditions for stopping the code (changing attributes, adding / removing descendants, deleting an. Hit on the resume button to continue running the script.If you need to debug a piece of code that handles DOM changes, the developer tool provides you with a way to stop code execution when a DOM node changes. Then use the developer tools to give you a breakdown of what is happening at that point.

Same Origin Policy & Cross-Origin Communication The Chrome Developer Tools helps web developers to access the internals. The ellipsis menu on the right-hand side of Developer Tools contains several commands that let you perform actions or change tool settings.Chrome Developer Tools are debugging & Web authoring tools built into Google Chrome.

Developer ToolsThe second option is to add a breakpoint directly into the code from the browser's Developer Tools. Once the JS interpreter reaches that line, it will stop the script execution, allowing you to inspect variables and step through your code. From an Integrated Development Environment (IDE).You can place a debugger statement anywhere in your JavaScript code. From the browser, using the Developer Tools. From code, using the debugger statement. You can then step through the program line by line, observing its execution and inspecting the contents of your variables.There are three ways of creating breakpoints.

Open the 'Scripts' folder in the left-side panelAdding a breakpoint from the Developer ToolsOnce you have your JavaScript file open in Developer Tools, you can click a line number to place a breakpoint. Press Command+ Option+ C to open Developer Tools Use the folder icon near the upper-left corner of the window to open a file-selection pane you can find your JavaScript file there. Press Ctrl+ P and type the name of your JavaScript file Switch to the Sources tab (Chrome) or Debugger tab (Firefox)

To delete the breakpoint, click the red circle again.Tip: You can also utilise the conditional breakpoints in browser's dev tools. Run the code from VSC by pressing the green play button or hit F5.Click next to the line number in your JavaScript source file to add a breakpoint (it will be marked red). If not already done, create a launch configuration file ( launch.json) by pressing the gear icon. Click the Debug button on the left or Ctrl+ Shift+ D IDEs Visual Studio Code (VSC)VSC has built-in support for debugging JavaScript. In Chrome, this is done by clicking on the button in the bottom right corner of the source code viewer.

Interactive interpreter variablesNote that these only work in the developer tools of certain browsers.$_ gives you the value of whatever expression was evaluated last. To do that, right click the DOM node on the Elements tab and select 'Break on.'. The button can be found near Execution Controls and is useful for locating errors.You can also pause execution when an HTML tag (DOM node) is modified, or when its attributes are changed. Shortcut : Shift + F11(Chrome, Firefox, IE/Edge), F8(Safari)Use these in conjunction with the Call Stack, which will tell you which function you're currently inside of, which function called that function, and so forth.See Google's guide on 'How to Step Through the Code' for more details and advice.Links to browser shortcut key documentation:In Google Chrome, you can pause execution without needing to place breakpoints.Pause on Exception: While this button is toggled on, if your program hits an unhandled exception, the program will pause as if it had hit a breakpoint. Shortcut : F11(Chrome, Firefox, IE/Edge), F7(Safari)Step Out: Run the rest of the current function, jump back to where the function was called from, and pause at the next statement there.

You can check if your JS is manipulating DOM the way you expect it to, Var images = $$('img') // Returns an array or a nodelist of all matching elementsВ№ alias to either document.getElementById or document.querySelector Elements inspectorClicking the Select an element in the page to inspect it button in the upper left corner of the Elements tab in Chrome or Inspector tab in Firefox, available from Developer Tools, and then clicking on a element of the page highlights the element and assigns it to the $0 variable.Elements inspector can be used in variety of ways, for example: This is essentially a shortcut for document.querySelectorAll. So if is highlighted: $0 // $1 refers to the element previously selected, $2 to the one selected before that, and so forth for $3 and $4.To get a collection of elements matching a CSS selector, use $$(selector).

You can play around with CSS and HTML without reloading the page.

How To Use F12 Debugger