How is it possible for the output to be a string array when the variable was declared as a number in TypeScript?

Question

How is it possible for the output to be a string array when the variable was declared as a number in TypeScript?

Snippet:

function sampleFunction(sample:string|number|string[])
{
    if(typeof sample == "string")
    {
        console.log("Sample is String " + sample);
    }
    else if(typeof sample == "number")
    {
        console.log("Sample is Number " + sample);
    }
    else{
        console.log("Sample is String Array " + sample);
    }
}
var sample:number; //Assigning the variable as a number
sampleFunction(sample);

Console Output:

Sample is String Array undefined

Even though the var type is specified as "number", why does the output show "String array"?

javascript angular typescript

Answer 1

Answer №1

The variable example has not been assigned a value, so by default it is considered as undefined, which explains why the final else statement in your code is being executed.

You can resolve this issue by setting the value of example before calling the function:

var example = 10;
test(example);
// Output will be: Number 10

Keep in mind that type declarations are utilized during compilation and do not impact the runtime behavior of your code.

Answer 2

The variable example has not been assigned a value, so by default it is considered as undefined, which explains why the final else statement in your code is being executed.

You can resolve this issue by setting the value of example before calling the function:

var example = 10;
test(example);
// Output will be: Number 10

Keep in mind that type declarations are utilized during compilation and do not impact the runtime behavior of your code.

Answer 3

Answer №2

While you've initialized a number variable, it's important to remember that without assigning a value to the variable, it will default to undefined in TypeScript. The properties you define for the variable will actually be properties of the value assigned to it, not the variable itself.

Answer 4

While you've initialized a number variable, it's important to remember that without assigning a value to the variable, it will default to undefined in TypeScript. The properties you define for the variable will actually be properties of the value assigned to it, not the variable itself.

Answer 5

Answer №3

When working with TypeScript, we have the ability to assign a "type" to a variable from the beginning. However, it is important to remember that TypeScript files are ultimately converted into JavaScript for browser compatibility. If a variable is declared without a value in TypeScript, it defaults to undefined when executed.

For example, declaring var example:number; assigns a type to the variable but does not provide a value. As a result, the variable will be undefined at runtime, leading to the last else condition being triggered and printing:

Example is String Array undefined

.

Answer 6

When working with TypeScript, we have the ability to assign a "type" to a variable from the beginning. However, it is important to remember that TypeScript files are ultimately converted into JavaScript for browser compatibility. If a variable is declared without a value in TypeScript, it defaults to undefined when executed.

For example, declaring var example:number; assigns a type to the variable but does not provide a value. As a result, the variable will be undefined at runtime, leading to the last else condition being triggered and printing:

Example is String Array undefined

.

Answer 7

Answer №4

Instead of passing an example variable that doesn't contain a value in the function, try passing a number. This might result in a string array type being displayed. The reason for this is that when it's undefined, the typeof undefined doesn't correspond to either a string or number, leading the code to execute the else block.

Answer 8

Instead of passing an example variable that doesn't contain a value in the function, try passing a number. This might result in a string array type being displayed. The reason for this is that when it's undefined, the typeof undefined doesn't correspond to either a string or number, leading the code to execute the else block.

How is it possible for the output to be a string array when the variable was declared as a number in TypeScript?

Answer №1

Answer №2

Answer №3

Answer №4

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