I happened to know the following code
Here is the code, and very simple:
var test = 0 || -1 ;
console.log(test);
then the output in the console is -1
and somehow i am really new into the javascript,
all i think of is that the 0 stands for Boolean False in JS ,and so || operator seems to ignore the 0 and assign the value -1 to the variable
so am i right ? i just want a confirm
|| — expr1 || expr2 (Logical OR)
Returns expr1 if it can be converted to true; otherwise, returns expr2. Thus, when used with Boolean values, || returns true if either operand is true; if both are false, returns false..
&& — expr1 && expr2 (Logical AND)
Returns expr1 if it can be converted to false; otherwise, returns expr2. Thus, when used with Boolean values, && returns true if both operands are true; otherwise, returns false.
All values in Javascript are either "truthy" or "falsy".
The following values are equivalent to false in conditional statements:
"" (\ '')All other values are equivalent to true.
So... var test = 0 || -1 ; returns -1.
If it was var test = 0 || false || undefined || "" || 2 || -1 it would return 2
Logical operator on MDN
var user =function (ops) { return { firstName: ops.name || 'John', lastName: ops.name || 'Doe', email: ops.email || '[email protected]', name:function () {return this .firstName +this .lastName}}} -- So, I'm guessing it assigns the first values if they're "truthy" (defined) else the second values are defaults?
You can use Nullish coalescing operator (??)
The nullish coalescing operator (??) is a logical operator that returns its right-hand side operand when its left-hand side operand is null or undefined, and otherwise returns its left-hand side operand.
Only null and undefined will be falsey. 0 will be considered true. But take care: an empty string will be considered true too!
console.log('0 ?? 1 ->', 0 ?? 1) // expected output: 0
console.log('null ?? 1 -> ', null ?? 1) // expected output: 1
console.log('undefined ?? 1 ->', undefined ?? 1) // expected output: 1
console.log('"" ?? 1 ->', "" ?? 1) // expected output: ""