Javascript Data Types | Primary Data Types | Composite Data Types | Unique Data Types | Learn Javascript

Javascript Data Types | Primary Data Types | Composite Data Types | Unique Data Types | Learn Javascript

Javascript Data Types | Primary Data Types | Composite Data Types | Unique Data Types | Learn Javascript


Data type of JavaScript

In JavaScript, there are three essential information sorts, two composite information sorts, and two exceptional information sorts.

Primary Data Types

The essential (primitive) information sorts are:




Composite data type

The composite (reference) information sorts are:



Unique Data Types

The unique information sorts are:



String Data Type

A string esteem is a chain of at least zero Unicode characters (letters, digits, and accentuation marks). You utilize the string information sort to speak to content in JavaScript. You incorporate string literals in your contents by walling them in single or twofold quotes. Twofold quotes can be contained in strings encompassed by single quotes, and single quotes can be contained in strings encompassed by twofold quotes. The accompanying are cases of strings:



“Cheerful am I; from mind I’m free!”

‘”Avast, ye loafers!” thundered the expert.’



Notice that JavaScript does not have a sort to speak to a solitary character. To speak to a solitary character in JavaScript, you make a string that comprises of just a single character. A string that contains zero characters (“”) is an unfilled (zero-length) string.

JavaScript gives escape groupings that you can incorporate into strings to make characters that you can’t sort straightforwardly. For instance, \t indicates a tab character. For more data, see Special Characters.

Number Data Type

In JavaScript, there is no refinement amongst whole number and skimming point esteems; a JavaScript number can be either (inside, JavaScript speaks to all numbers as gliding point esteems).

Number Values

Number esteems can be sure entire numbers, negative entire numbers, and 0. They can be spoken to in base 10 (decimal), base 16 (hexadecimal), and base 8 (octal). Most numbers in JavaScript are composed in decimal.

You indicate hexadecimal (“hex”) whole numbers by prefixing them with a main “0x” (zero and x|X). They can contain digits 0 through 9, and letters A through F (either capitalized or lowercase) as it were. The letters A through F are utilized to speak to, as single digits, 10 through 15 in base 10. That is, 0xF is identical to 15, and 0x10 is comparable to 16.

You signify octal numbers by prefixing them with a main “0” (zero). They can contain digits 0 through 7 as it were. A number that has a main “0” and contains the digits “8” or potentially “9” is translated as a decimal number.

Both hexadecimal and octal numbers can be negative, yet they can’t have a decimal bit, and they can’t be composed in logical (exponential) documentation.


Beginning in Internet Explorer 9 principles mode, Internet Explorer 10 benchmarks mode, Internet Explorer 11 guidelines mode, and Windows Store applications, the parseInt work does not treat a string that has a prefix of “0” as octal. When you are not utilizing the parseInt work, be that as it may, strings with a prefix of “0” can in any case be deciphered as octal.

Drifting point Values

Drifting point esteems can be entire numbers with a decimal part. Also, they can be communicated in logical documentation. That is, a capitalized or lowercase “e” is utilized to speak to “ten to the energy of”. JavaScript speaks to numbers utilizing the eight byte IEEE 754 skimming point standard for numerical portrayal. This implies you can compose numbers as vast as 1.79769×10308, and as little as 5×10-324. A number that contains a decimal point and that has a solitary “0” preceding the decimal point is translated as a decimal skimming point number.

Notice that a number that starts with “0x” or “00” and contains a decimal point will create a blunder. Here are a few cases of JavaScript numbers.

Number Description Decimal Equivalent

.0001, 0.0001, 1e-4, 1.0e-4 Four proportionate drifting point numbers. 0.0001

3.45e2 A gliding point number. 345

45 An integer. 45

0378 An whole number. In spite of the fact that this resembles an octal number (it starts with a zero), 8 is not a substantial octal digit, so the number is dealt with as a decimal. 378 Javascript Data Types

0377 An octal whole number. Notice that in spite of the fact that it just seems, by all accounts, to be one not as much as the number over, its genuine esteem is very different. 255

0.0001 A drifting point number. Despite the fact that this starts with a zero, it is not an octal number since it has a decimal point. 0.0001

00.0001 This is a blunder. The two driving zeros stamp the number as an octal, yet octals are not permitted a decimal component. N/A (compiler mistake)

0Xff A hexadecimal integer. 255

0x37CF A hexadecimal integer. 14287

0x3e7 A hexadecimal whole number. Notice that the “e” is not regarded as exponentiation. 999

0x3.45e2 This is a blunder. Hexadecimal numbers can’t have decimal parts. N/A (compiler mistake)

Also, JavaScript contains numbers with exceptional esteems. These are:

NaN (not a number). This is utilized when a scientific operation is performed on unseemly information, for example, strings or the unclear esteem

Positive Infinity. This is utilized when a positive number is too substantial to speak to in JavaScript

Negative Infinity. This is utilized when a negative number is too extensive to speak to in JavaScript

Positive and Negative 0. JavaScript separates amongst positive and negative zero.

Boolean Data Type

Though the string and number information sorts can have an essentially boundless number of various esteems, the Boolean information sort can just have two. They are the literals genuine and false. A Boolean esteem is a reality esteem: it indicates whether the condition is valid or not.

Examinations you make in your contents dependably have a Boolean result. Consider the accompanying line of JavaScript code.



y = (x == 2000);

Here, the estimation of the variable x is contrasted with the number 2000. On the off chance that it is, the aftereffect of the examination is the Boolean esteem genuine, which is alloted to the variable y. On the off chance that x is not equivalent to 2000, at that point the aftereffect of the examination is the Boolean esteem false.

Boolean esteems are particularly valuable in control structures. The accompanying code joins an examination that makes a Boolean esteem straightforwardly with an announcement that utilizations it. Consider the accompanying JavaScript code test.



on the off chance that (x == 2000) {

z = z + 1;


else {

x = x + 1;


The if/else proclamation in JavaScript performs one activity if a Boolean esteem is valid (z = z + 1), and a substitute activity if the Boolean esteem is false (x = x + 1).

You can utilize any articulation as a similar articulation. Any articulation that assesses to 0, invalid, indistinct, or a vacant string is deciphered as false. An articulation that assesses to some other esteem is translated as genuine. For instance, you could utilize an articulation, for example,



/This may not do what you anticipate. See underneath!

on the off chance that (x = y + z)

Note that the above line does not check whether x is equivalent to y + z, since just a solitary equivalent sign (the task administrator) is utilized. Rather, the code above allots the estimation of y + z to the variable x, and afterward checks whether the consequence of the whole articulation (the estimation of x) is zero. To check whether x is equivalent to y + z, you have to utilize the accompanying code.



/This is not the same as the code above!

in the event that (x == y + z)

For more data on correlations, see Controlling Program Flow.

The invalid Data Type

The invalid information sort has just a single an incentive in JavaScript: invalid. The invalid watchword can’t be utilized as the name of a capacity or variable.

A variable that contains invalid contains no substantial Number, String, Boolean, Array, or Object. You can eradicate the substance of a variable (without erasing the variable) by allotting it the invalid esteem.

Notice that in JavaScript, invalid is not the same as 0 (as it is in C and C++). Additionally take note of that the typeof administrator in JavaScript reports invalid esteems as being of sort Object, not of sort invalid. This conceivably confounding conduct is for in reverse similarity.

The unclear Data Type

The unclear esteem is returned when you utilize a protest property that does not exist, or a variable that has been pronounced, however has never had an esteem appointed to it.

you can verify whether a variable exists by contrasting it with indistinct, in spite of the fact that you can check if its sort is unclear by contrasting the kind of the variable with the string “vague”. The accompanying case demonstrates to discover the variable x has been pronounced:



var x;

/This technique works.

on the off chance that (x == indistinct) {

document.write(“comparing x to unclear <br/>”);



/This technique doesn’t work – you should check for the string “indistinct”.

on the off chance that (typeof(x) == indistinct) {

document.write(“comparing the kind of x to indistinct <br/>”);


/This technique works.

on the off chance that (typeof(x) == “unclear”) {

document.write(“comparing the kind of x to the string ‘undefined'”);



/contrasting x with indistinct

/contrasting the kind of x with the string “unclear”

You can likewise contrast the indistinct incentive with invalid. This examination is valid if the property someObject.prop is invalid or if the property someObject.prop does not exist.



someObject.prop == invalid;

To see if a protest property exists, you can utilize the in administrator:



on the off chance that (“prop” in someObject)

/someObject has the property “prop”

See Also

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About Ashok.cse

Hi, I'm currently studying for the Bachelor of Technology In Computer Science from Rajasthan Technical University. I am the web developer with 3+ years of experience. my range of developer services including creating the design for new apps and web platforms or building UI design for mobile, tablets or desktops. making UX designs wireframes and layouts concepts and redesigns websites are adapting to mobile and responsive design. I have worked with many clients. I am working professionally with WordPress And Adobe tools.

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