![]() ![]() It is also possible to manually raise an error of using the “throw” statement. However, if the code is wrapped in a try block, the execution will jump to the catch block if an exception is thrown and the program will continue as normal. Normally program execution stops when an error is thrown by the JavaScript engine. In JavaScript the try…catch statement allows programmers to handle errors in the code. It will step into a function line by line.Ĥ️⃣ Step out: Executes the remaining code in the current function, and pauses when the runtime returns to the line of code after the function was called. It steps over a function without debugging the individual steps of the function.ģ️⃣ Step into: Executes the next line of code and then pauses on the following line. ![]() The execution can proceed in the sine of the following ways.ġ️⃣ Resume Script Execution: Resumes execution until the program hits another breakpoint or the program ends.Ģ️⃣ Step-Over: Executes the next line of code in a single step and then pauses on the following line. The JavaScript engine pauses the execution of code when it hits a breakpoint. The scope pane is only populated with variables when the script is being debugged. The local and global sections under this show the variables that are defined in the current scope. In the “Sources” tab, the window on the right contains the scope. On the left is a list of all the source files used by the HTML document. The debugger makes it possible to step through the code line by line to see what is happening to the variables as the code executes. The JavaScript debugger can be found under the Sources tab. The “Console” tab contains two areas:ġ️⃣ Console Output log: Displays system and user messages from the JavaScript execution.Ģ️⃣ Console Command Line Interface: Accepts any JavaScript instructions and executes them immediately. Web Developers can output messages to the console log to make sure their code is executing as expected. To open the developer tools for the Google Chrome browser, press Command+Option+I (Mac) & Control+Shift+I (Windows, Linux). The developer tools contain functionality to debug JavaScript and view the state of HTML elements in the browser. Developer ToolsĪll modern browsers contain a set of developer tools to help programmers work with HTML, CSS, and JavaScript. ![]() Newer versions of JavaScript do not throw this error. A URlError is thrown when there is a problem encoding or decoding a URI because of the use of a reserved character.ĥ️⃣ ReferenceError This error occurs when the code refers to a variable that either does not exist or is not in scope for the executing code.Ħ️⃣ EvalError This error occurs when there is a problem with the eval() function. For example, applying the string.substring method to a variable that is a number.ģ️⃣ RangeError When the code attempts to use a number that is outside the range of possible values, JavaScript detects a RangeErrorĤ️⃣ URIError Some alphanumeric characters are not allowed to be used in a URL. This error occurs while the JavaScript engine is interpreting the code at run time.Ģ️⃣ TypeError This error occurs when the wrong data type is used. Errors in JavaScriptġ️⃣ Synta圎rror An error in the way the code is written causes a syntax error. Since JavaScript is interpreted at run time and executed inside the browser, debugging is performed with tools built into the browser. Debugging slows down the JavaScript execution and shows how data is modified line by line. ![]() Programmers spend a lot of time diagnosing and remedying errors and omissions in their code. ![]()
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