Javascript Flashcards
Write:
How to include a javascript file?
Is JS a dynamic language?
If so, what does that entail?
It is a dynamic language. As such, the value of the variables can be modified at runtime
What are the three ways to declare variables?
let, var and const
What happens if a variable is created without being declared?
They are global
What happened if a variable is not assigned a value?
Its value is “undefined”
What is a Falsy value?
What are the falsy values?
A value that is not false, but would be false in a Boolean context
undefined, NaN, null, “”, 0
What happens if we try to + a string and a number?
The number is coerced to a string.
What are the five primitive data types in JS?
Number, String, Boolean, null and undefined
What are the comparison rules for < and >
1-If one is a number and the other can be converted: comparison
2-If one is a number and the other one cannot be converted: false
3-If both are strings: string comparison
What are the comparison rules for all the other operators (asterisk, /, %)
If one cannot be converted to a number: NaN
What are the two types of equality operators, and how do they differ?
The loose equality (==, !=) and the strict equality (===, !==). The former does type coercion, the latter does not
For the variable declarator “let”, tell us about its scope, whether it can be redeclared and whether a value must be declared at creation.
Block scope, cannot be redeclared and does not have to be assigned a value at declaration
For the variable declarator “const”, tell us about its scope, whether it can be redeclared and whether a value must be declared at creation.
Block scope, cannot be redeclared and must be assigned a value at declaration
For the variable declarator “var”, tell us about its scope, whether it can be redeclared and whether a value must be declared at creation.
Global scope, can be redeclared and can also be declared before use
How to traverse all properties in an object?
for (x in object){…}
How to create an object?
var object = new Object();
Write
What are the two ways to create properties in an object?
either myobj.prop1=… or var myobj={prop1: …, prop2:…};
Write
What are the two ways to create arrays?
var myArray = [1, 2, 3]
var myArray = new Array(1,2,”3”)
What does .join do on an Array?
Array.join(“;”) for example, separates all the elements of the array by ; and returns it
What does Array.toString() do?
It concatenates the array and separates it with commas (like .join(“,”) would)
What does .slice() do?
It cuts a part of the array, from the first integer (inclusive) to the second integer (exclusive)
What is the difference between actual parameters and formal parameters?
Formal parameters are those written in the function creation while actual parameters are those used in the function call
Write
A sorting function to sort numbers, as well as its call
function sortNumber(a,b){
return a-b;
}
document.write(array.sort(sortNumber));
Write
How to write an anonymous function?
var f = function (a,b) {return a-b};
What happens if the prototype of an object is modified?
It changes the template of all objects of this type
Write
A constructor for a car object and the subsequent creation of a car object.
function car(make, year, model) {
this.make=make;
this.year=year;
this.model=model;
}
let car1 = new car(“Ford”, “2017”, “Fiesta”);
Write
For the car constructor, write a display function and add it to the constructor
function displayCar(){
document.write(“Year: “+this.year);}
this.display=displayCar; (to add to the constructor, since functions can be passed as parameters)
