Is there a way to use a logical operator for object properties? For example, can I do something like:
var myObj = {};
var prop = myObj.prop || 0;
Where prop gets set to 0 if prop isn't a property of myObj? But here,
var myObj = {};
myObj.prop = 2;
var prop = myObj.prop || 0;
myObj.prop is set to 2 because prop exists in this case.
No, but you can use the ternary conditional operator for it:
var has = Object.prototype.hasOwnProperty;
var prop = has.call(myObj, 'prop') ? 0 : undefined;
It is not perfect (future references to prop will no longer be a ReferenceError in the event that myObj does not have a prop property), but there is no better way without using let:
if (!has(...)) {
let prop = 0;
// Do things with `prop` here
}
// prop is still a ReferenceError outside of the if block
var prop = myObj.hasOwnProperty('prop') ? myObj.prop : 0
myObj = Object.create(null) this will break - don't make unguarded references to things on Object.prototype.
var has = Object.prototype.hasOwnProperty; var prop = has.call(myObj, 'prop') ? 0 : undefined; I get ReferenceError: myObj is not defined. The OP did include var myObj = {}; as the first line.var myObj = /* whatever you want on this side */ out of my answer to focus on the solution I was suggesting, but if you add the variable, everything will work, even if you use Object.create(null) as the value of myObj.var myObj = {}; since it's already in the OP's question.You could do something like this. You can use hasOwnProperty method to check that object has property or not
var myObj = {};
var prop = myObj.hasOwnProperty('prop') || 0;
prop to the value of myObj.prop if it does exist.var myObj = Object.create(null) the next line will fail - best to use Object.prototype.hasOwnProperty instead.A simpler varient would be to set the property in your fallback
var prop = myObject.prop || (myObject.prop = 0);
propset to 0 ifmyObj1) doesn't have a property of its own namedprop, 2) doesn't have a property anywhere in its prototype chain namedpropor 3) has a property namedprop(either in the sense of #1 or #2) but it is falsey?