I will ask my question using the following example:
HTML
<div>
<input id="ABC" placeholder="abc"></input>
<textarea id="XYZ" placeholder="xyz"></textarea>
</div>
JS Code
var valArray = [{id: "ABC", value: "INPUT"}, {id: "UNKNOWN", value: ""}, {id: "XYZ", value: "TEXTAREA"}]
function process(arr) {
for(var i=0; i<arr.length; i++) {
var elem = document.getElementById(arr[i].id);
if (elem != null) {
elem.value = arr[i].value;
}
}
}
process(valArray);
It works fine, but now I want to do it without an explicit if statement.
How about the following code? Is it a proper JavaScript way to handle such situations?
function process(arr) {
for(var i=0; i<arr.length; i++) {
(document.getElementById(arr[i].id) || 0).value = arr[i].value;
}
}
From Programming JavaScript Applications by Eric Elliott- Chapter 3. Objects:
Even primitive types get the object treatment when you refer to them with the property access notations. They get automatically wrapped with an object so that you can call their prototype methods.
Primitive types behave like objects when you use the property access notations, but you can't assign new properties to them. Primitives get wrapped with an object temporarily, and then that object is immediately thrown away. Any attempt to assign values to properties will seem to succeed, but subsequent attempts to access that new property will fail.
In general I saw a lot of JavaScript code where || <default or alternative value> construct was used to protect against null.
So I thought, that the above described behavior would make primitives ideal candidates for "throw-away" objects.
If this is so convoluted, what about using Object:
(document.getElementById(arr[i].id) || Object).value = arr[i].value;
That was my original idea but it seems to pollute the environment.
