Im trying to use typeof to determine whether or not a variable is undefined:
function reset_textarea(reset) {
if (typeof(reset) != 'undefined') {
...do stuff
}
}
Im calling it like this:
reset_textarea('hello');
Its not working and I can't seem to figure out why. The function fires normally if I remove the if statement, thus - the issue seems to lie in the way I am testing whether or not the variable is set. Any idea what is going on?
Well, typeof("hello")
(type of string ) is defined. It's a String
. typeof(hello)
(note missing quotes) is what you need. Does this work for you?
if(typeof(window[reset]) !== 'undefined') {
//...
}
You must understand the difference between a variable ( hello
) and a string ( "hello"
). Remember that window["hello"]
is equivalent to window.hello
, but more flexible.
You can test for the existence of a property with the specified name on window
:
function reset_textarea(reset) {
if (typeof(window[reset]) !== 'undefined') {
// ...do stuff
}
}
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