JavaScript – ECMAScript Basics By Satyen

JavaScript – ECMAScript Basics By Satyen

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  By: Satyen Pandya1JavaScript– ECMAScript Basicssatu21@gmail.com
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  Contents2 Syntax, Variables, Keywords, Reserved Words
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  Primitive and Reference Values
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  Primitive Types
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  Conversions
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  Reference Types
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  Operators
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  Statements
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  Functionssatu21@gmail.com
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  Syntax3 ECMAScript basic concepts :
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  Everything is case-sensitive
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  Variables are loosely typed
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  End-of-line semicolons are optional
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  Comments are the same as in Java, C, Perl
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  Braces indicate code blockssatu21@gmail.com
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  Variables4 Variables are defined by var operator
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  Variables do not require initialization like JAVA
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  Variables can hold different types of values at different times Variable name –
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  First character must be letter, an underscore (_)\ or dollar sign ($) Remaining characters may be underscores, dollarsings or any alphanumeric characters Variable should follow –
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  Camel Notation (e.g. myTest, myVar)
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  Pascal Notation (e.g. MyTest, MyVar)
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  Hungarian Type Notation (e.g. sMyTest, bMyVar)satu21@gmail.com
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  Keywords5 Keyword used to indicate beginning and/or endingof statements Keywords are reserved, can not use as variable or function name Few Keywords :satu21@gmail.com
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  Reserved Words6 Word that are reserved for future use as keyword
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  Can not use as variable or function name
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  Few Reserved words :satu21@gmail.com
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  Primitive and ReferenceValues7Primitive values - simple piece of data, stored on stack, the value is stored directly in location that variable accesses Reference values - objects, stored in heap, the value is stored in variable location – pointer, where the object is storedsatu21@gmail.com
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  Primitive Types8 ECMAScript has five primitive types :Undefined, Null, Boolean, Number, Stringtypeof Operator used to determine the type variable’svaluetypeof Operator takes one argument
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  typeof returns oneof below value :
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  “undefined”, “boolean”, “number”,“string”, “object”satu21@gmail.com
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  Conversions9 Type conversion is a short, one-step process in ECMAScript
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  Converting to astring : var.toString()
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  Converting to a number :var a = parseInt(“123”);var b = parseFloat(“123.456”);Type Casting : Boolean(value); Number(value); String(value);satu21@gmail.com
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  Reference Types10 They are referred as class, when you have a reference value, you are dealing with an object Objects are created by new operator and class namee.g. varobj = new Object(); Few classes :The Object classThe Boolean classThe Number classThe String classThe instanceof operatorsatu21@gmail.com
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  Reference Types (Contd…)11Theobject class : base class for all ECMAScript classes
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  All the properties and methods of Object class also present in other classes Properties :
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  constructor
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  Prototype
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  Methods :
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  hasOwnProperty(property)
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  isPrototypeof(object)
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  propertyIsEnumerable(property)
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  toString()
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  valueOf()satu21@gmail.com
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  Reference Types (Contd…)12TheBoolean class : reference type for Boolean type
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  pass only Boolean value
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  toString() – returnstrue or false
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  valueOf() – returnstrue or false
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  The Number class : reference type for Number type
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  pass only Boolean value
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  toString() – returnsnumber primitive value
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  valueOf() – returnsnumber primitive value
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  toFixed() – returnsstring representation of number
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  toExponential – returnse-notation string
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  toPrecision – returnsfixed or e-notation of numbersatu21@gmail.com
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  Reference Types (Contd…)13TheString class : reference type for String type
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  pass only Boolean value
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  toString() – returnsstring primitive value
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  valueOf() – returnsstring primitive value
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  length – gives number of characters
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  charAt() – returnsstring containing character in position
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  charCodeAt() – returnscharacter code
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  concat() – concatetwo or more strings
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  indexOf() – returnsposition of given substring
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  lastindexOf() – returnslast position of given substring
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  The instanceof operator: identifies the type of objectsatu21@gmail.com
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  Operators14Unary operators :
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  delete – erases reference to an object property or method
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  void – returns undefined for any value
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  prefix increment/decrement (e.g. ++a, --a)
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  postfix increment/decrement (e.g. a++, a--)
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  unary plus – returns exact same value for integer, for string it converts them to numbers unary minus – returns negative value for integer, for string it negates the valuesatu21@gmail.com
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  Operators (Contd…)15Bitwise operators:
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  Bitwise NOT – tilde(~), it works in 3 stpesOperand is converted to 32-bit numberBinary form converted into its one’s complementOne’s complement is converted back to number Bitwise AND – ampersand(&)
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  works directly on the binary form of numbers
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  Bitwise OR – pipe(|)
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  works directly on the binary form of numbers
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  Bitwise XOR – caret(^)
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  works directly on the binary form of numberssatu21@gmail.com
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  Operators (Contd…)16Bitwise operators:satu21@gmail.com
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  Operators (Contd…)17Boolean operators:
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  Logical NOT – exclamation(!), always return Boolean
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  Logical AND – double ampersand(&&)
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  Logical OR – double pipe(||)satu21@gmail.com
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  Multiplicative operators18Multiply :represented by asterisk(*)
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  Divide : represented by slash(/)
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  Modulus : represented by percent sign(%)Additive operatorsAdd : represented by plus(+)
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  Subtract : represented by minus(-)
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  Modulus : represented by percent sign(%)satu21@gmail.com
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  Relational operators19less-than :represented by <
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  greater-than : represented by >
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  less-than-or-equal : represented by <=
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  greater-than-or-equal : represented by >=Equality operatorsEqual : represented by double equal sign (==)
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  Not Equal : represented by exclamation with equal sign (!=)
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  Identically equal :three equal sign (===)
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  Not identically equal: exclamation and two equal (!==)satu21@gmail.com
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  Conditional operators20 Syntax :Variable = boolean_expression ? true_value : false_value; if expression is true then true_value will be assigned, else false_value will be assignedAssignment operators Simple assignment operator (=) assings the value on the right to the variable on the leftComma operators more than one operation in single linesatu21@gmail.com
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  Thank you…By: SatyenPandya21satu21@gmail.com