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Andersonb-JavaScript

Beg Java Script Vocab

TermDefinition
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).
Booleans Syntax true false
Boolean logical operators if ( true && false )alert("Not executed!"); //because the second expression is false
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
== vs. === A simple explanation would be that == does just value checking ( no type checking ) , whereas , === does both value checking and type checking . Seeing the examples may make it all clear. It is always advisable that you never use ==
Note An important thing to note here is that not only Boolean literals (true and false) assert truth or false , but there are some other ways too to derive true or false.Have a look at the examples.
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. Comments are like notes , suggestions , warnings ,etc. that you can put for yourself.
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 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.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
console.timeEnd Stops a timer that was previously started by calling console.time().
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.
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
Do While Loops You use do while loops, if you have to loop at least once, but if you don't know how often.
Math random umber 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 simple math
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 obj['name']; // 'Bob' obj.name; // 'Bob' obj.getAge(); // 24
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 if ( confirm("Are you sure you want to delete this post?") ) { deletePost(); }
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 "some" + "text"; // returns "sometext" var first = "my"; var second = "string"; var union = first + second; // union variable has the string "mystring"
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. 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
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 cts like a big if / else if / else chain. Checks a value against a list of cases, and executes the first case that is true. It goes on executing all other cases it finds after the first true case till it finds a breaking statemen
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: 2015andersonb