• Some JavaScript libraries relies on window innerWidth and innerHeight to do their calculations


• 
  window.innerWidth is not 100% reliable, which may lead to bugs


• 
  matchMedia().matches is 100% accurate but it returns a boolean value


• come around: use matchMedia to verify window.innerWidth value; if it returns false use matchMedia to do a binary search until it finds the correct value

I faced that issue with some libs that relies on window.innerWidth. In cases where I had some media queries the return value of window.innerWidth used by the library would be off and that library would have issues with incorrect value.

I've seen that matchMedia().matches always return the correct value, but it returns a boolean value, not the width value. I've not seen a solution so far for that (maybe some of you know a better solution?), so I came up with a solution using matchMedia.

I created a function getCorrectDimension that performs a binary search around the window innerWidth (or innerHeight) to find the correct value if its value is wrong as you can see below:

const binarySearch = dim => function bin(start, end) 
 const guess = Math.floor((start + end)/2)

 // this checks if we have the correct value, if not it will keep calling itself until there's a match
 if(window.matchMedia(`($dim: $guesspx)`).matches) 
 return guess
 

 // since it is not a match, then we need to recalibrate the range and call again.
 // for that we check the boolean value using with min-width (height) rule.
 return window.matchMedia(`(min-$dim: $guesspx)`).matches 
 ? bin(guess, end) 
 : bin(start, guess)


const getCorrectDimension = (dim = 'width', range = 300) => 
 if(dim !== 'width' && dim !== 'height') 
 throw Error('`getCorrectDimension` accepts "width" or "height" as parameter')
 

 let prop = 'inner' + dim.charAt(0).toUpperCase() + dim.slice(1)

 // here checks if the window.innerWidth or Height it's the correct one
 if(window.matchMedia(`($dim: $window[prop]px)`).matches) 
 return window[prop]
 

 // here, since the value is wrong we use binarySearch to find its correct value
 const start = window[prop] - range >= 0 ? window[prop] - range : 0
 const end = window[prop] + range

 return binarySearch(dim)(start, end)

I have never seen innerWidth or innerHeight report the wrong value. There are a few bugs listed for chrome and firefox but they are all closed.

Could you provide any evidence?

UPDATE

Media query matches down to fractions of a CSS pixel while innerWidth returns integer CSS pixel values. This is a problem when devicePixelRatio !== devicePixelRatio | 0

I tried to find a cover all solution, but too much time need to complete so I withdraw the answers content.