Whenever vm8 encounters a property that doesn't exist, it will display an error message like this:
Cannot read property 'value' of null. For example, when passing an id that doesn't exist:
var pass = document.getElementById('pass');
if (pass.value == '') // An error occurs due to the null property
My question is: How can we prevent the compiler from encountering this line of code with a proper condition? Thank you
// Locate the element.
// If the specified element is not found, it will return as `null`
var pass = document.getElementById('pass');
if (pass) {
alert(pass.value);
} else {
alert("Element could not be located. There seems to be an issue.');
}
The statement: if (pass) can also be expressed as if (pass !== null), but it serves no additional purpose.
Opt for if (pass.value == ''), consider
if (typeof(pass.value) == 'undefined')
There are multiple methods to achieve this:
if(typeof(pass.value) === 'undefined')
if(typeof(pass)==="undefined")
if('value' in pass)
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