JSON.stringify doesn’t directly work with sets because the data stored in the set is not stored as properties. But you can convert the set to an array. Then you will be able to stringify it properly. Any of the following will do the trick: JSON.stringify([…s]); JSON.stringify([…s.keys()]); JSON.stringify([…s.values()]); JSON.stringify(Array.from(s)); JSON.stringify(Array.from(s.keys())); JSON.stringify(Array.from(s.values()));
This has nothing to do with Traceur and turning something off; this is simply how ES6 works. It’s the specific functionality you’re asking for by using => instead of function () { }. If you want to write ES6, you need to write ES6 all the time. You can’t switch in and out of it … Read more
According MDN documentation: A Map object iterates its elements in insertion order. You could do it this way: var map = new Map(); map.set(‘2-1’, “foo”); map.set(‘0-1’, “bar”); map.set(‘3-1′, “baz”); var mapAsc = new Map([…map.entries()].sort()); console.log(mapAsc) Using .sort(), remember that the array is sorted according to each character’s Unicode code point value, according to the string … Read more
[…nodelist] will make an array of out of an object if the object is iterable. Array.from(nodelist) will make an array out of an object if the object is iterable or if the object is array-like (has .length and numeric props) Your two examples will be identical if NodeList.prototype[Symbol.iterator] exists, because both cases cover iterables. If … Read more
You can use Array.from or spread syntax (…). Example: const x = new Set([ 1, 2, 3, 4 ]); const y = Array.from(x); console.log(y); // = [ 1, 2, 3, 4 ] const z = [ …x ]; console.log(z); // = [ 1, 2, 3, 4 ]
You can use setStateinside componentDidUpdate. The problem is that somehow you are creating an infinite loop because there’s no break condition. Based on the fact that you need values that are provided by the browser once the component is rendered, I think your approach about using componentDidUpdate is correct, it just needs better handling of … Read more
You forgot to close the Class bracket. class AddAddressComponent extends React.Component { render() { let {provinceList,cityList} = this.props if(cityList === undefined || provinceList === undefined){ console.log(‘undefined props’) } else { console.log(‘defined props’) } return ( <div>rendered</div> ) } } AddAddressComponent.contextTypes = { router: React.PropTypes.object.isRequired }; AddAddressComponent.defaultProps = { cityList: [], provinceList: [], }; AddAddressComponent.propTypes = … Read more
The issue stems from the {…} operators having multiple meanings in JavaScript. When { appears at the start of a Statement, it’ll always represent a block, which can’t be assigned to. If it appears later in the Statement as an Expression, then it’ll represent an Object. The var helps make this distinction, since it can’t … Read more
Your state needs some time to mutate, and since console.log(this.state.boardAddModalShow) executes before the state mutates, you get the previous value as output. So you need to write the console in the callback to the setState function openAddBoardModal() { this.setState({ boardAddModalShow: true }, function () { console.log(this.state.boardAddModalShow); }); } setState is asynchronous. It means you can’t … Read more
It appears I cannot use an if statement. Arrow functions either allow to use an expression or a block as their body. Passing an expression foo => bar is equivalent to the following block foo => { return bar; } However, if (person.age > 18) person is not an expression, if is a statement. Hence … Read more