Sneaky bugs: using lodash/trimStart to trim off a leading substring

Sneaky bugs are bugs that escape your first glance through the code. I’ve had this recently happen to me with lodash/trimStart.

trimStart removes leading whitespace or passed in characters until it hits a character that isn’t one of the characters to trim. In this case it was used to remove a substring from the beginning of the input string.

  trimStart('Mr. Mario', 'Mr. ') // expected: 'Mario', actual: 'ario'
  trimStart('+919999999999', '+91') // expected: '9999999999', actual: ''

You’re better off using replace with startsWith to do the job.

  const inputStr = 'Mr. Mario'
  const subStr = 'Mr. '
  startsWith(inputStr, subStr) && replace(inputStr, subStr, '') // expected: 'Mario', actual: 'Mario'

This wouldn’t necessarily happen to someone who’s familiar with lodash/trimStart but it certainly sneaked past me.