Getting the first index of an object
Just for fun this works in JS 1.8.5 var obj = {a: 1, b: 2, c: 3}; Object.keys(obj)[0]; // “a” This matches the same order that you would see doing for (o in obj) { … }
javascript-objects
Using curl POST with variables defined in bash script functions
You don’t need to pass the quotes enclosing the custom headers to curl. Also, your variables in the middle of the data argument should be quoted. First, write a function that generates the post data of your script. This saves you from all sort of headaches concerning shell quoting and makes it easier to read … Read more
Create an empty object in JavaScript with {} or new Object()?
Objects There is no benefit to using new Object(); – whereas {}; can make your code more compact, and more readable. For defining empty objects they’re technically the same. The {} syntax is shorter, neater (less Java-ish), and allows you to instantly populate the object inline – like so: var myObject = { title: ‘Frog’, … Read more
How to do a deep comparison between 2 objects with lodash?
An easy and elegant solution is to use _.isEqual, which performs a deep comparison: var a = {}; var b = {}; a.prop1 = 2; a.prop2 = { prop3: 2 }; b.prop1 = 2; b.prop2 = { prop3: 3 }; console.log(_.isEqual(a, b)); // returns false if different <script src=”https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.min.js”></script> However, this solution doesn’t show which … Read more
How to get all properties values of a JavaScript Object (without knowing the keys)?
Depending on which browsers you have to support, this can be done in a number of ways. The overwhelming majority of browsers in the wild support ECMAScript 5 (ES5), but be warned that many of the examples below use Object.keys, which is not available in IE < 9. See the compatibility table. ECMAScript 3+ If … Read more
How to return value from an asynchronous callback function? [duplicate]
This is impossible as you cannot return from an asynchronous call inside a synchronous method. In this case you need to pass a callback to foo that will receive the return value function foo(address, fn){ geocoder.geocode( { ‘address’: address}, function(results, status) { fn(results[0].geometry.location); }); } foo(“address”, function(location){ alert(location); // this is where you get the … Read more
How to iterate over a JavaScript object?
For iterating on keys of Arrays, Strings, or Objects, use for .. in : for (let key in yourobject) { console.log(key, yourobject[key]); } With ES6, if you need both keys and values simultaneously, do for (let [key, value] of Object.entries(yourobject)) { console.log(key, value); } To avoid logging inherited properties, check with hasOwnProperty : for (let … Read more
__proto__ VS. prototype in JavaScript
__proto__ is the actual object that is used in the lookup chain to resolve methods, etc. prototype is the object that is used to build __proto__ when you create an object with new: ( new Foo ).__proto__ === Foo.prototype ( new Foo ).prototype === undefined
From an array of objects, extract value of a property as array
Here is a shorter way of achieving it: let result = objArray.map(a => a.foo); OR let result = objArray.map(({ foo }) => foo) You can also check Array.prototype.map().
How can I display a JavaScript object?
Use native JSON.stringify method. Works with nested objects and all major browsers support this method. str = JSON.stringify(obj); str = JSON.stringify(obj, null, 4); // (Optional) beautiful indented output. console.log(str); // Logs output to dev tools console. alert(str); // Displays output using window.alert() Link to Mozilla API Reference and other examples. obj = JSON.parse(str); // Reverses … Read more