function indexOf(subject, search, fromIndex) {
    var subjectString = coerceToString(subject);
    return subjectString.indexOf(search, fromIndex);
  }
Returns the first occurrence index of `search` in `subject`.

@function indexOf
@static
@since 1.0.0
@memberOf Index
@param {string} [subject=''] The string where to search.
@param {string} search The string to search.
@param {number} [fromIndex=0] The index to start searching.
@return {number} Returns the first occurrence index or `-1` if not found.
@example
v.indexOf('morning', 'n');
// => 3

v.indexOf('evening', 'o');
// => -1