set variable and use it in function in javascript

In JavaScript, you can declare a variable using the var, let, or const keywords. The var keyword is used for declaring variables in the global scope or function scope, while let and const are used for block scope.

To set a variable and use it in a function, you can declare the variable outside the function and then pass it as a parameter to the function. Alternatively, you can declare the variable inside the function using var, let, or const.

Here's an example of setting a variable and using it in a function using parameters:

index.tsx
var myVariable = "Hello, world!";

function myFunction(variable) {
  console.log(variable);
}

myFunction(myVariable); // Output: "Hello, world!"
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And here's an example of setting a variable and using it in a function by declaring it inside the function:

index.tsx
function myFunction() {
  var myVariable = "Hello, world!";
  console.log(myVariable);
}

myFunction(); // Output: "Hello, world!"
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Note that in the second example, the variable myVariable is only accessible inside the myFunction function due to scoping.