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Qu<|repo_name|>jasonzhangai/django-notes<|file_sep|>/content/posts/2020-10-07-javascript-tips.md --- title: JavaScript Tips You Should Know date: '2020-10-07' spoiler: 'This post contains tips which can help improve your JavaScript code' category: programming tags: - javascript --- ## Use `const` whenever possible You should always use `const` instead of `let` when declaring variables. This will prevent accidental reassignment. js // bad practice let x = 'foo'; x = 'bar'; // good practice const x = 'foo'; ## Use strict equality operators (`===`, `!==`) instead of abstract equality operators (`==`, `!=`) Strict equality operators compare both value **and** type whereas abstract equality operators only compare values. Using strict equality operators will help prevent unexpected behavior due to type coercion. js // bad practice if (x == '5') { // ... } // good practice if (x === '5') { // ... } ## Avoid using global variables Global variables can lead to naming conflicts between different parts of your codebase. Instead try using local variables within functions or modules. js // bad practice var globalVar = 'global'; function foo() { console.log(globalVar); } foo(); // logs 'global' // good practice function bar() { const localVar = 'local'; console.log(localVar); } bar(); // logs 'local' ## Use arrow functions instead of traditional function expressions Arrow functions provide a concise syntax that makes them easier to read than traditional function expressions. They also don't have their own `this` context which makes them useful when working with callbacks. js // bad practice function add(a,b) { return a + b; } add(1); // returns NaN because b defaults undefined // good practice (using arrow function) const add = (a,b) => a + b; add(1); // returns NaN because b defaults undefined still but now we get an error message telling us what went wrong! ## Don't use `eval()`! Using `eval()` allows executing arbitrary code which could potentially lead security vulnerabilities such as XSS attacks. If you really need dynamic code execution then consider using [new Function()][new-function]. [new-function]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_objects/Function/new_function js // bad practice (using eval()) const userInput = prompt('Enter some JavaScript code:'); eval(userInput); // good practice (using new Function()) const userInput = prompt('Enter some JavaScript code:'); new Function(userInput)(); --- I hope these tips help improve your JavaScript code! If you have any questions feel free [to contact me][contact]. [contact]: mailto:[email protected]