Quick Reference
The in operator returns “true” if the specified property is in the specified object, or “false” if it is not.
// array
const my_cars = ['Lamborghini', 'Ferrari', 'Maserati', 'Alfa Romeo'];
'Maserati' in my_cars // returns false (specify the index not the value)
0 in my_cars // returns true
1 in my_cars // returns true
4 in my_cars // returns false (does not exist)
'length' in my_cars // returns true (length is an Array property)
// object
const my_family = {first_name:'Johnny', age:9};
'first_name' in my_family // returns true
'age' in my_family // returns trueJavaScript Notes:
- When using JavaScript, single or double quotation marks are acceptable and work identically to one another; choose whichever you prefer, and stay consistent
- JavaScript is a case-sensitive language; firstName is NOT the same as firstname
- Arrays count starting from zero NOT one; so item 1 is position [0], item 2 is position [1], and item 3 is position [2] … and so on
- JavaScript variables must begin with a letter, $, or _
- JavaScript variables are case sensitive (x is not the same as X)
We’d like to acknowledge that we learned a great deal of our coding from W3Schools and TutorialsPoint, borrowing heavily from their teaching process and excellent code examples. We highly recommend both sites to deepen your experience, and further your coding journey. We’re just hitting the basics here at 1SMARTchicken.