tl;dr class C defines a class, just as in Java or C++. object O creates a singleton object O as instance of some anonymous class; it can be used to hold static members that are not associated with instances of some class. object O extends T makes the object O an instance of trait T; … Read more
>>> class Test: … def __repr__(self): … return “Test()” … def __str__(self): … return “member of Test” … >>> t = Test() >>> t Test() >>> print(t) member of Test The __str__ method is what gets called happens when you print it, and the __repr__ method is what happens when you use the repr() function … Read more
ECMAScript 6 introduces the easily polyfillable Object.assign: The Object.assign() method is used to copy the values of all enumerable own properties from one or more source objects to a target object. It will return the target object. Object.assign({}, [‘a’,’b’,’c’]); // {0:”a”, 1:”b”, 2:”c”} The own length property of the array is not copied because it … Read more
Use the super() function: class Foo(Bar): def baz(self, **kwargs): return super().baz(**kwargs) For Python < 3, you must explicitly opt in to using new-style classes and use: class Foo(Bar): def baz(self, arg): return super(Foo, self).baz(arg)
How about with some es6 magic? obj.arr = obj.arr.filter((value, index, self) => index === self.findIndex((t) => ( t.place === value.place && t.name === value.name )) ) Reference URL A more generic solution would be: const uniqueArray = obj.arr.filter((value, index) => { const _value = JSON.stringify(value); return index === obj.arr.findIndex(obj => { return JSON.stringify(obj) === _value; … Read more
var myProp = ‘prop’; if(myObj.hasOwnProperty(myProp)){ alert(“yes, i have that property”); } Or var myProp = ‘prop’; if(myProp in myObj){ alert(“yes, i have that property”); } Or if(‘prop’ in myObj){ alert(“yes, i have that property”); } Note that hasOwnProperty doesn’t check for inherited properties, whereas in does. For example ‘constructor’ in myObj is true, but myObj.hasOwnProperty(‘constructor’) … Read more
var obj = { first: ‘someVal’ }; obj[Object.keys(obj)[0]]; //returns ‘someVal’ Object.values(obj)[0]; // returns ‘someVal’ Using this you can access also other properties by indexes. Be aware tho! Object.keys or Object.values return order is not guaranteed as per ECMAScript however unofficially it is by all major browsers implementations, please read https://stackoverflow.com/a/23202095 for details on this.
If you want to avoid external libraries, you can concisely implement a vanilla version of groupBy() like so: var groupBy = function(xs, key) { return xs.reduce(function(rv, x) { (rv[x[key]] = rv[x[key]] || []).push(x); return rv; }, {}); }; console.log(groupBy([‘one’, ‘two’, ‘three’], ‘length’)); // => {3: [“one”, “two”], 5: [“three”]}
You have to do it step by step if you don’t want a TypeError because if one of the members is null or undefined, and you try to access a member, an exception will be thrown. You can either simply catch the exception, or make a function to test the existence of multiple levels, something … Read more
The iteration order for objects follows a certain set of rules since ES2015, but it does not (always) follow the insertion order. Simply put, the iteration order is a combination of the insertion order for strings keys, and ascending order for number-like keys: // key order: 1, foo, bar const obj = { “foo”: “foo”, … Read more