Q631. What is the purpose of exec method?
The purpose of exec method is similar to test method but it executes a search for a match in a specified string and returns a result array, or null instead of returning t...
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Q632. What is React memo function?
Class components can be restricted from re-rendering when their input props are the same using **PureComponent or shouldComponentUpdate**. Now you can do the same with fu...
Q633. How do you change the style of a HTML element?
You can change inline style or classname of a HTML element using javascript DOM-manipulation 1. **Using style property:** You can modify inline style using style property...
Q634. What would be the result of 1+2+'3'?
The output is going to be `33`. Since `1` and `2` are numeric values, the result of the first two digits is going to be a numeric value `3`. The next digit is a string ty...
Q635. How to prevent unnecessary updates using setState?
You can compare the current value of the state with an existing state value and decide whether to rerender the page or not. If the values are the same then you need to re...
Q636. What is a debugger statement?
The debugger statement invokes any available debugging functionality, such as setting a breakpoint. If no debugging functionality is available, this statement has no effe...
Q637. How do you render Array, Strings and Numbers in React 16 Version?
**Note:** This question references React 16. These features remain valid in current React versions (18/19). **Arrays**: Starting with React 16, you can return multiple si...
Q638. What is the purpose of breakpoints in debugging?
You can set breakpoints in the javascript code once the debugger statement is executed and the debugger window pops up. At each breakpoint, javascript will stop executing...
Q639. Can I use reserved words as identifiers?
No, you cannot use the reserved words as variables, labels, object or function names. Let's see one simple example, ```javascript var else = "hello"; // Uncaught SyntaxEr...
Q640. How do you detect a mobile browser?
You can use regex which returns a true or false value depending on whether or not the user is browsing with a mobile. ```javascript window.mobilecheck = function () { var...