What are the data types of JS?
undefined
null
boolean
string
symbol
number
object
What is the initial value of a JS variable? undefined
What is the result of doing a math operation on undefined? NaN
What is the result of concatenating a string with undefined? "undefined"
What is the % operator called? remainder operator
Why is the % operator not called modulus operator? It does not work properly with negative numbers
How do I add an element to the end of an array? array.push(value);
How do I remove the last element of an array? array.pop();
How do I remove the first element of an array? array.shift();
How do I add an element to the start of an array? array.unshift(value)
The visibility of variables.
What value does a function return if it does not have a return statement? undefined
Do comparison operators do type coercion? Yes!
1 != "1" // false
7 > '3' // true
What kind of equality do switch statements use? Strict equality
What is the format of a switch statement? switch(value) {
case value1:
statements;
break;
...
default:
defaultStatement;
break;
}
Can you use numbers as object properties? Yes! But JS will typecast them as strings.
var anotherObject = {
5: "five",
};
Can you omit quotes for string properties? Yes, but only for single-word properties
var anotherObject = {
make: "Ford"
};
How do I delete a property from a JS object? delete object.property
How do I determine if an object has a property? object.hasOwnProperty(property)
How do I generate a random number? Math.random()
How do I get the floor of a number? Math.floor(number)
How do I parse an integer from a string? parseInt(string)
What are the components of recursive function?