Cathal Cathal - 15 days ago 5
Javascript Question

return a string based on conditions without using if/else

I have an object something like

const myObj = {
hasError: true/false,
someProp: 'someValue'
}


Based on this object I have four conditions to evaluate:


  1. Object is empty

  2. hasError is true

  3. has error is false and someProp is undefined

  4. has error is false and some prop is defined



I'd like to find a nice and readable way to evaluate these 4 conditions without resorting to if/else.

Any ideas greatly appreciated.

Answer

Write the conditions and ensuing actions as an array of condition/action tuples:

const actions = [
  {if: o => !Object.keys(o).length, then: () => console.log("empty")},
  {if: o => o.hasError,             then: () => console.log("hasError")},
  {if: o => !o.someProp,            then: () => console.log("someProp is undefined")},
  {if: o => true,                   then: () => console.log("got everything")}
];

Now find the first matching condition and execute the associated logic:

actions.find(action => action.if(myObj)).then()

If it is not guaranteed that at least one condition will be satisfied, then you would need to check the result of the find to make sure it's not null.