Term | Definition |
Array literals | You can create arrays in two different ways. The most common of which is to list values in a pair of square brackets. JavaScript arrays can contain any types of values and they can be of mixed types. |
Accessing array elements | You can get elements out of arrays if you know their index. Array elements' indexes start at 0 and increment by 1, so the first element's index is 0, the second element's index is 1, the third element's is 2, etc. |
Multi-dimensional Arrays | A two-dimensional array is an array within an array. If you fill this array with another array you get a three-dimensional array and so on. |
Array constructor | You can also create an array using the Array constructor. |
Accessing nested array elements | Accessing multi dimensional array elements is quite similar to one-dimension arrays . They are accessed by using [index][index]..... (number of them depends upon the number of arrays deep you want to go inside). |
Boolean literals | not only Boolean literals (true and false) assert truth or false , but there are some other ways too to derive true or false. |
Boolean logical operators | expressions |
Comparison operators | uses x and y |
Code Comments | Code comments are used for increasing the readability of the code.Comments are like notes , suggestions , warnings ,etc. that you can put for yourself. Code comments are not executed |
Single Line Comment | Anything on the line following // will be a comment while anything before will still be code. |
Multi-Line Comment | Anything between /* and */ will be a comment. |
console.log | Prints text to the console. Useful for debugging. |
console.time | This function starts a timer which is useful for tracking how long an operation takes to happen. |
console.time continued | You give each timer a unique name, and may have up to 10,000 timers running on a given page.When you call console.timeEnd() with the same name, the browser will output the time, in milliseconds, that elapsed since the timer was started. |
console.timeEnd | Stops a timer that was previously started by calling console.time(). |
Function | A function is a JavaScript procedure—a set of statements that performs a task or calculates a value. |
Function calling | functionName(argument1, argument2, ..., argumentN); |
Function hoisting | The two ways of declaring functions produce different results. Declaring a function one way "hoists" it to the top of the call, and makes it available before it's actually defined. |
if | It simply states that if this condition is true , do this , else do something else ( or nothing ) . It occurs in varied forms. |
else | A fallback to an if statement. This will only get executed if the previous statement did not. |
else if | This is like an else statement, but with its own condition. It will only run if its condition is true, and the previous statement's condition was false. |
For Loops | You use for loops, if you know how often you'll loop. The most often used varName in loops is "i". |
While Loops | You use while loops, if you don't know how often you'll loop. |
Do While Loops | You use do while loops, if you have to loop at least once, but if you don't know how often. |
random | Returns a random number between 0 and 1. |
floor | Returns the largest integer less than or equal to a number. |
pow | Returns base raised to exponent. |
ceil | Returns the smallest integer greater than or equal to a number. |
PI | Returns the ratio of the circumference of a circle to its diameter, approximately 3.14159 or in better terms, the value of PI (π). Note in syntax , we do not put `()` at the end of `Math.PI` because `Math.PI` is not a function. |
sqrt | Returns the square root of a number. |
% (Modulus) | it returns the remainder left after dividing the left hand side with the right hand side. |
isNaN | Returns true if the given number is not a number , else returns false. |
Basic Arithmetic | Doing basic arithmetic is simple. |
Prefix and Postfix increment/decrement operators | Prefix increment / decrement operators are operators that first increase the value of the variable by 1 (increment) or decrease the value of an expression / variable by 1 (decrement) and then return this incremented / decremented value. |
Object Literals | {
"property 1": value1,
property2: value2,
number: value3
} |
Property Access | name1[string]
name2.identifier |
Classes | A class can be thought of as a template to create many objects with similar qualities. Classes are a fundamental component of object-oriented programming (OOP). |
alert | Display an alert dialog with the specified message and an OK button. Note: The alert dialog should be used for messages which do not require any response on the part of the user, other than the acknowledgement of the message. |
confirm | confirm("message") //returns true if confirmed, false otherwise |
prompt | The prompt() displays a dialog with an optional message prompting the user to input some text. If the user clicks the "Cancel" button , null is returned. |
Strings | Strings are text. They are denoted by surrounding text with either single or double quotes. |
Concatenation | string1 + string2 |
length | Returns the length of the string. |
toUpperCase, toLowerCase | Changes the cases of all the alphabetical letters in the string. |
trim() | Removes whitespace from both ends of the string. |
replace() | Returns a string with the first match substring replaced with a new substring. |
charAt() | Returns the specified character from a string.Characters in a string are indexed from left to right. |
charAt() continued | The index of the first character is 0, and the index of the last character in a string called stringName is stringName.length - 1. If the index you supply is out of range, JavaScript returns an empty string. |
substring() | Returns the sequence of characters between two indices within a string. |
indexOf() | Returns the index within the calling String object of the first occurrence of the specified value, starting the search at fromIndex, Returns -1 if the value is not found. The indexOf method is case sensitive. |
switch | Acts like a big if / else if / else chain. Checks a value against a list of cases, and executes the first case that is true. |
switch continued | It goes on executing all other cases it finds after the first true case till it finds a breaking statement,after which it breaks out of the switch If it does not find any matching case , it executes the default case. |
Ternary Operator | The ternary operator is usually used as a shortcut for the if statement. |
Variable Assignment | var name = value; |
Variable changing | varname = newValue |