30 bytes to coerce "23" to Number, keep "apple" as String

coerce.js

/**
 * function coerce(x) {
 *   return ''+x===x?(p=~~+x?r=+x:r=x):r=x
 * }
 * > undefined
 * coerce(123)
 * > 123
 * coerce('123')
 * > 123
 * coerce('apple')
 * > "apple"
 * coerce(2.343344555)
 * > 2.343344555
 * coerce('2.3243499348')
 * > 2.3243499348
 */
''+x===x?(p=~~+x?r=+x:r=x):r=x

''+x === x
? (
    p = ~~+x
    ? r = +x
    : r = x
  )
: r = x