Special operators
Contents
- 1. The list of special operators
- 2. Ternary operator ? :
- 3. Operator in
- 4. Operator instanceof
- 5. Operator new. Create an object instance
- 6. Operator this. Get the current object
- 7. Operator typeof. Get the type as a string
- 8. Operator void. Perform calculation without returning a value
- 9. Operator ‘ , ‘ (comma). Initialization of multiple variables, multiple assignments
- Related topics
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1. The list of special operators
In JavaScript, special operators perform all sorts of important functions. These operators include:
- conditional operator ?:. This operator is also called a ternary operator because it requires three operands to produce a result;
- operator delete;
- operator in;
- operator instanceof;
- operator new;
- operator this;
- operator typeof;
- operator void;
- operator ‘ , ‘ (comma).
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2. Ternary operator ? :
Ternary operator ?: uses three operands to produce a result. General form of using the operator
res = condition ? expression1 : expression2
here
- condition – conditional expression, the result of which is true or false;
- expression1 – expression to be calculated if condition = true;
- expression2 – expression to be calculated if condition = false;
- res is the result obtained as a result of evaluating one of the expressions expression1 or expression2.
The ternary operator ?: can be replaced by an if-else statement.
Example.
// Ternary operator ?: // 1. Calculate the maximum of two numbers x, y var x, y var res1 x = 8 y = 5 res1 = (x > y) ? x : y // res1 = x = 8 // 2. Get notification about string equality/inequality var s1 = "abcd" var s2 = "abcde" var res2 = (s1 == s2) ? "Strings are equal." : "Strings are not equal"
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3. Operator in
The in operator is intended to determine whether a given value exists in an object. General form of using the operator
value in obj
here
- obj – an object;
- value – the value to check for in the obj object.
The result of the operator’s work can be true or false.
Example.
// Operator in // Checking if the Days array contains an element with index 5 var Days = [ "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday" ]; if (5 in Days) { document.write("Index 5 is in the array Days.") } else { document.write("Index 5 is not in the array Days.") }
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4. Operator instanceof
The instanceof operator allows you to determine whether the specified object is of a given type. General form of using the operator
obj instanceof type
here
- obj – an instance (object) of some type;
- type – any type (Number, String, …).
Example.
// Operator instanceof 'use strict'; // 1. String type // Create an object of type String var str = new String() if (str instanceof String) document.write("str is of type String") else document.write("str is not of type String") // 2. The object of type Number var x = Number(10) if (x instanceof Number) document.write("x is of type Number") else document.write("x is not of type Number")
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5. Operator new. Create an object instance
The new operator is for creating an instance of an object. The operator has the following general usage form
obj = new Type()
here
- Type – some type. It can be one of the standard types (Number, String, and others) or a type defined by programmer;
- obj is the name of the object for which the instance is being created.
Example.
// Operator new // Create an object of type Number var num = new Number(23) // Create an object of type String var str str = new String("Hello")
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6. Operator this. Get the current object
The use of the this keyword depends on the context in which it is used. A detailed overview of the use of the this keyword in programs is beyond the scope of this topic.
This topic discusses the case of using this object to obtain a reference to this object. For this case, the using of this operator is as follows
this.item
Here item is some element of the object (variable, object, function, etc.).
Example.
'use strict'; var Point = { x: 10, y: 10, PrintX: function () { console.log("x = ", this.x) // this - a reference to a Point object }, PrintY: function () { console.log("y = ", this.y) // this - a reference to a Point object }, PrintXY: function () { this.PrintX() // call methods of current object this.PrintY() } } var x = 5 Point.PrintX() // x = 10 var y = 55 Point.PrintY() // y = 10 Point.PrintXY()
Program result
x = 10 y = 10 x = 10 y = 10
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7. Operator typeof. Get the type as a string
Using the typeof operator, you can get the name of an object’s type as a string. General form of using the operator
typeName = typeof(obj)
here
- obj – an object;
- typeName – a string type variable containing the type name of the obj object.
Example.
'use strict'; // typeof operator - get a string representation of a type var Line = { x1: 10, y1: 10, x2: 20, y2: 25, Length: function () { return len = Math.sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2)); } } var typeName = typeof(Line) // typeName = "object" console.log(typeName) var t = 77 typeName = typeof (t) // typeName = "number" console.log(typeName) var s = "Hello!" typeName = typeof (s) // typeName = "string" console.log(typeName)
Program result
object number string
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8. Operator void. Perform calculation without returning a value
Evaluation of an operand expression without returning a value is performed by the void operator. The void operator evaluates the given expression and returns undefined. The general form of using the operator
void expression
here
- expression – expression or function.
Example.
The example shows the use of the void operator for a function and an expression.
'use strict'; // Operator void // 1. Using void with function // Function that does not return anything void function Hello() { console.log("Hello, world!") }() // 2. Using void with an expression var b = void (2 == '2') // b = undefined console.log("b = ", b) var res = void (25 * 3) // res = undefined console.log("void (25*3) => ", res) res = void 25 * 3 // res = NaN console.log("void 25*3 => ", res)
Program result
Hello, world! b = undefined void (25*3) => undefined void 25*3 => NaN
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9. Operator ‘ , ‘ (comma). Initialization of multiple variables, multiple assignments
The ‘ , ‘ operator is used to perform multiple assignments, other operations within loops, or initialization of variables.
Example.
'use strict'; // Operator , (comma) // 1. Initialization of variables var x = 5, y = 8 console.log("x = ", x, "; y = ", y) // 2. Initializing an array with values var A = [2, 3, 3, 4] console.log("A = ", A) // 3. Several assignments var a, b, c a = 3, b = 7, c = 11 console.log("a = ", a, ", b = ", b, ", c = ", c) // 4. Using a comma in a loop // Output the squares of numbers from 1 to 5 in the original way for (var i = 1, j = 1; i <= 5, j <= 5; i++, j++) console.log(i * j)
Result
x = 5 ; y = 8 A = [ 2, 3, 3, 4 ] a = 3 , b = 7 , c = 11 1 4 9 16 25
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Related topics
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