Beg Java Script Vocab
Quiz yourself by thinking what should be in
each of the black spaces below before clicking
on it to display the answer.
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| 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.
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| 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.
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| 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.
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| Array constructor | You can also create an array using the Array constructor.
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| 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).
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| Booleans | Syntax
true
false
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| Boolean logical operators | if ( true && false )alert("Not executed!");
//because the second expression is false
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| 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
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| == 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 ==
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| 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.
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| 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.
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| Single Line Comment | Anything on the line following // will be a comment while anything before will still be code.
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| Multi-Line Comment | Anything between /* and */ will be a comment.
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| console | Prints text to the console. Useful for debugging.
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| 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
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| console.timeEnd | Stops a timer that was previously started by calling console.time().
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| 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.
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| 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
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| Do While Loops | You use do while loops, if you have to loop at least once, but if you don't know how often.
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| Math | random umber between 0 and 1
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| floor | Returns the largest integer less than or equal to a number.
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| pow | Returns base raised to exponent.
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| ceil | Returns the smallest integer greater than or equal to a number.
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| 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
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| sqrt | Returns the square root of a number.
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| % (Modulus) | it returns the remainder left after dividing the left hand side with the right hand side.
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| isNaN | Returns true if the given number is not a number , else returns false.
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| Basic Arithmetic | simple math
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| 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.
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| Object Literals | {
"property 1": value1,
property2: value2,
number: value3
}
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| Property Access | obj['name']; // 'Bob'
obj.name; // 'Bob'
obj.getAge(); // 24
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| 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).
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| 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.
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| confirm | if ( confirm("Are you sure you want to delete this post?") ) {
deletePost();
}
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| 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.
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| Strings | Strings are text. They are denoted by surrounding text with either single or double quotes
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| Concatenation | "some" + "text"; // returns "sometext"
var first = "my";
var second = "string";
var union = first + second; // union variable has the string "mystring"
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| length | Returns the length of the string.
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| toUpperCase, toLowerCase | Changes the cases of all the alphabetical letters in the string.
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| trim() | Removes whitespace from both ends of the string.
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| replace() | Returns a string with the first match substring replaced with a new substring
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| 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
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| substring() | Returns the sequence of characters between two indices within a string.
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| 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.
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| 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
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| Ternary Operator | The ternary operator is usually used as a shortcut for the if statement.
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| Variable Assignment | var name = value;
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| Variable changing | varname = newValue
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Or sort by any of the columns using the down arrow next to any column heading.
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