How to Declare a Variable in Javascript
The process of creating a variable is also known as declaring a variable.,var age; , called age., You can declare more than one variable by separating each with a comma and still use one var command, as: ,var state, city, zip, country; , When you...
Step-by-Step Guide
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Step 1: The process of creating a variable is also known as declaring a variable.
When you declare a variable, you tell the computer to reserve some memory for your program to store some data.
To declare a variable in JavaScript, use the var command.
For instance, the following command creates a variable -
Step 2: var age;
, With the above command, computer will reserve some memory and allow you to store to or retrieve from that memory with the name you chose, age.
Remember at this point our variable age is null or has a garbage value–whatever computer's memory slot happens to hold. ,,,, Examples of reserved words in JavaScript include var, or document.write.
Basically, reserved words have a specific purpose in JavaScript, they cannot be used as a variable name. , age, year, _month are all valid variable names.
However, 11month, 9_ are not valid variable names. , If your variable consists of more than one word, separate each word with an underscore (i.e., first_name, last_name) or use camel case (i.e., firstName, lastName). , In JavaScript, a variable named first_name is considered different from first_Name or FIRST_name. , Avoid using a variable name such as k, l, m, z, or a because you may have hard time figuring out what each variable represent in the future or in a long program. ,, In JavaScript, however, you can also declare variables implicitly by using the assignment operator to assign a value to the new variable.
For example, ,,,,,,,,,,, -
Step 3: called age.
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Step 4: You can declare more than one variable by separating each with a comma and still use one var command
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Step 5: var state
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Step 6: country;
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Step 7: When you declare a variable
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Step 8: keep the following JavaScript restrictions in mind to a variable name:
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Step 9: A variable name cannot be one of the reserved words in JavaScript.
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Step 10: The first letter of a variable name must be a letter or an underscore (_).
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Step 11: A variable name cannot contain any space characters.
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Step 12: Remember that variable names are case-sensitive.
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Step 13: keep your variable names meaningful.
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Step 14: Declaring variable without var command
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Step 15: As noted above
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Step 16: to explicitly declare (create) a variable in JavaScript we use the var command.
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Step 17: age = 50;
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Step 18: declares a variable called age and signs he integer value 50 to this variable.
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Step 19: The following shows some more examples of variables being created when a value is assigned to a variable:
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Step 20: <script language="javascript">
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Step 21: sum = x = y = 0; // declares three variables and each is set to 0.
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Step 22: </script>
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Step 23: Alternatively
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Step 24: you may declare and assign the values using the var command:
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Step 25: <script language="javascript">
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Step 26: var sum
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Step 27: y; // declares multiple variable with the var command.
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Step 28: sum = x = y = 0; // sets each variable to 0
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Step 29: </script> Datatypes in Javascript are : String Number Boolean Function Array Object
Detailed Guide
When you declare a variable, you tell the computer to reserve some memory for your program to store some data.
To declare a variable in JavaScript, use the var command.
For instance, the following command creates a variable
, With the above command, computer will reserve some memory and allow you to store to or retrieve from that memory with the name you chose, age.
Remember at this point our variable age is null or has a garbage value–whatever computer's memory slot happens to hold. ,,,, Examples of reserved words in JavaScript include var, or document.write.
Basically, reserved words have a specific purpose in JavaScript, they cannot be used as a variable name. , age, year, _month are all valid variable names.
However, 11month, 9_ are not valid variable names. , If your variable consists of more than one word, separate each word with an underscore (i.e., first_name, last_name) or use camel case (i.e., firstName, lastName). , In JavaScript, a variable named first_name is considered different from first_Name or FIRST_name. , Avoid using a variable name such as k, l, m, z, or a because you may have hard time figuring out what each variable represent in the future or in a long program. ,, In JavaScript, however, you can also declare variables implicitly by using the assignment operator to assign a value to the new variable.
For example, ,,,,,,,,,,,
About the Author
Jesse Perry
A seasoned expert in education and learning, Jesse Perry combines 2 years of experience with a passion for teaching. Jesse's guides are known for their clarity and practical value.
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