Variable is a name of identifier which is capable to hold some value and reference. Value of variable are access by its name. The typeScript variable is based on the data type. Which are as follows.
|number||TypeScript supports 64 bit numbers.|
|boolean||Represents a boolean value either true or false|
|string||String is combination of single and more characters.|
|void||Its used for functions that return nothing|
|null||Represents no value or null value of objects|
let and var keyword is used to declare variable in typescript. Here let indicate constant variable the value are never change. and var keyword are used to declare a mutable variable. Its syntax as follows.
// Declaring variable without value var variableName : dataType ; or // Variable with initial value let/var variableName : dataType = initialValue;
For example, let's create some variables using this data type.
// Declare string variable var name: string ; // Declare number variable var price: number ; // Declare boolean variable var status: boolean ; // Display default value of variable console.log("name : ", name); console.log("price : ", price); console.log("status : ", status); // Change variable value name = "ABC"; price = 342.45; status = true; // Display variable value console.log("name : ", name); console.log("price : ", price); console.log("status : ", status);
name : undefined price : undefined status : undefined name : ABC price : 342.45 status : true
There are three types of variable scopes are possible in typescript language.
Local Scope: This type of variable define within function and blocks. They are cannot access outside the function.
Global Scope: This type of variable define outside the function and its can be access all over the source code.
Class Scope : This is instance and field variable of class which is access by execute the class method and directly accessed by objects.