I am trying to do the following to satisfy the requirements of a code builder (Sencha Cmd to be specific).
This is the essence I what I need to do. The critical factor is that the function body MUST end with a return of an object literal. I cant return a variable due to restrictions in the builder. So, how to add a property 'b' at the point of the pseudo code below if the parameter 'includeB' is true, but NOT add a property AT ALL if it is false. ie b==undefined or b==null is not allowed.
Perhaps it is not possible.
function create(includeB) {
// Can have code here but the final thing MUST be a return of the literal.
// ...
return {
a : 1
// pseudo code:
// if (includeB==true) then create a property called b
// and assign a value of 2 to it.
// Must be done right here within this object literal
}
}
var obj = create(false);
// obj must have property 'a' ONLY
var obj = create(true);
// obj must have properties 'a' and 'b'
Thanks for reading and considering,
Murray
Create a pure function to return a new constant with the new object added to the array. Use a spread operator in the definition of the constant.
You can use an if statement, if it is within a immediately invoked function.
If you can use ES6, use the spread properties.
function create(includeB) {
return {
a : 1,
...(includeB ? { b: 2 } : {}),
};
}
You've pretty much shown a use case for a constructor function instead of using an object literal:
function CustomObject(includeB) {
this.a = 1;
if (includeB) {
this.b = 2;
}
}
//has `a` only
var obj1 = new CustomObject(false);
//has `a` and `b`
var obj2 = new CustomObject(true);
After re-reading your question it appears that you've got limited access in modifying the function. If I'm understanding your question correctly you can only change a limited portion of the script:
function create(includeB) {
// modifications may be done here
// the rest may not change
return {
a : 1
}
}
var obj = create(false);
// obj must have property 'a' ONLY
var obj = create(true);
// obj must have properties 'a' and 'b'
If that's the case, then you could simply skip the later part of the function:
function create(includeB) {
if (includeB) {
return {
a: 1,
b: 2
};
}
return {
a: 1
};
}
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