Is there a built-in way to test if a variable is of a specific type?

blackslate

The documentation indicates that there are 9 standard types:

• Boolean
• Number
• String
• Array
• Map
• Box
• Function
• Builtin
• Undefined

However, I have found no standard method to check if a given variable is of a given type. Have I not been looking hard enough?

I have found a workaround, by creating a `testType` function and overloading it for each type, so that the different overloaded versions return the name of the type that they receive as an argument.

function testType(value is array) {<br>&nbsp;&nbsp;&nbsp; return "array";<br>}<br><br>function testType(value is boolean) {<br>&nbsp;&nbsp;&nbsp; return "boolean";<br><div>}</div><div><br></div><div>// ... and so on<br><br>function isArray (value) {<br>    return (testType(value) == "array");<br>}<br></div>

(The Format > Code option makes the code above look terrible in Preview. Let's hope it appears correctly in the forum.)

You can find my proof of concept here.

Is my workaround really necessary, or is there a built-in method that I have overlooked?

ilya_baran

You can use the "is" operator, as in:

if (myVariable is array)
{
    // Handle array case
}

blackslate

Thanks Ilya.
Where is the "is" operator documented?

NeilCooke

https://cad.onshape.com/FsDoc/tokens.html
https://cad.onshape.com/FsDoc/type-tags.html

ilya_baran

You can use the "is" operator, as in:

if (myVariable is array)
{
    // Handle array case
}

blackslate

Thanks Ilya.
Where is the "is" operator documented?

NeilCooke

https://cad.onshape.com/FsDoc/tokens.html
https://cad.onshape.com/FsDoc/type-tags.html