JavaScript Tips
@javascript_tips
Tips and tricks to make the most of JavaScript and avoid gotchas.
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Arrow functions are not yet supported in Safari, IE and Opera Mini. #javascript #es6 #tip caniuse.com/#feat=arrow-fu…
// ES5 var posNums = nums.filter(function (x) { return x > 0; }); // #ES6 var posNums = nums.filter(x => x > 0); #javascript #tip
#ES6 arrow functions do not have their own 'this'. The value of this inside an arrow function is always inherited from the enclosing scope.
Code is temporary. It exists while it is useful. If code is replaced by better code, good! If code can be deleted, celebrate! #JavaScript
Shorthand for #es6 arrow function with single argument: var f = x => { return x*x; }; // equivalent to var f = (x) => { return x*x; };
Shorthand for #es6 arrow function with single return statement: var f = (x) => x*x; // equivalent to var f = (x) => { return x*x; };
ES6 arrow functions: var normalFunc = function(x) { return x * x; }; var arrowFunc = (x) => { return x*x; }; #javascript #tips
#javascript 'new' keyword: function A() { this.x = 1; this.y = 2; } var a1 = new A(); var a2 = new A(); a1.x++; a1.x; // 2 a2.x; // 1
Usage of the 'arguments' local variable: function foo() { console.log(arguments); } foo(1, 2, 3, 4); // [1, 2, 3, 4] #javascript #tip
Use #es6 in your javascript code today with @babeljs! hacks.mozilla.org/2015/06/es6-in…
Convert CSV to array: var str = "apple, peach, orange"; var fruitsArray = str.split(","); // ['apple', 'peach', 'orange'] #javascript #tip
#JavaScript array to csv: var fruits = ['apple', 'peaches', 'oranges']; var str = fruits.valueOf(); // apple,peaches,oranges #js #tips
Remove duplicates from array: var deduped = [ 1, 1, 'a', 'a'].filter(function (x, i, arr) { return arr.indexOf(x) === i; }); // [1, 'a']
Flattening an array : var myArray = [[1, 2], [], [3]]; var flatArray = [].concat.apply([], myArray); // flatArray is [1, 2, 3] #javascript
Getting a UNIX timestamp in #JavaScript: var dateTime = Date.now(); var timestamp = Math.floor(dateTime / 1000); #tips #js
To see a function's code, concatenate it with the empty string : console.log(funcVariable + ''); #javascript #tips
The && operator first evaluates the expression on the left. If falsy, false is returned; it does not bother to evaluate the right operand.
JavaScript Falsy Values: null, false, 0 undefined, NaN, and “” (this last item is an empty string). #javascript #tips
Infinity, which is a special number like NaN, is truthy; it is not falsy, while NaN is falsy. #javascript #tips
Calculate max/min in an array: var arr = [1, 2, 3, 4]; Math.max.apply(null, arr) // 4 Math.min.apply(null, arr) // 1 #javascript #tips
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