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# dharlow-JavaScript

### Beginning JavaScript Vocabulary

TermDefinition
Array Literals 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,indexes start at 0 and increment by 1
Multi-Dimensional Arrays The two-dimensional arrays are the arrays within arrays. If you fill this array with another array you get a three-dimensional array and so on and so forth
Array Constructor You can also create an array using the Array constructor
Accessing nested array elements They are accessed by using [index][index]..... (number of them depends upon the number of arrays deep you want to go inside).
Boolean Literals true or false
Boolean logical operators expression1 && expression2 //returns true if both the expressions evaluate to true expression3 || expression4 // return true if either one of the expression evaluates to true !expression5 // returns the opposite boolean value of the expression
Comparison Operators x === y // returns true if two things are equal x !== y // returns true if two things are not equal x <= y // returns true if x is less than or equal to y x >= y // returns true if x is greater than or equal to y
Note Not only Boolean literals (true and false) assert truth or false , but there are some other ways too to derive true or false. Such as,if(1)console.log("True!"); // output True! , since any non-zero number is considered to be true
== vs. === A simple explanation would be that == does just value checking ( no type checking ) , whereas , === does both value checking and type checking
Code Comments Code comments are used for increasing the readability of the code.If you write 100 lines of code and then forget what each function did , it's not useful at all
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 commen
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.timeEnd Stops a timer that was previously started by calling console.time().
Function definition 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 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
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.
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
Concatenation Strings are text
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.
chartAt() Returns the specified character from a 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.
Ternary Operator The ternary operator is usually used as a shortcut for the if statement.
Variable Assignment var name = value;
Variable changing varname = newValue
Created by: 2016harlowd