Object predicates for ko.utils.arrayFirst and similar

example.js

// Override arrayFirst (but remain backward compatible)
ko.utils._arrayFirst = ko.utils.arrayFirst
ko.utils.arrayFirst = function (array, ...predicateParams) {
  // In case used as regular arrayFirst
  if (typeof predicateParams[0] === 'function') {
    return ko.utils._arrayFirst(array, predicateParams[0])
  }
  // Otherwise wrap
  return ko.utils._arrayFirst(array, ko.utils.objectPredicate(...predicateParams))
}

ko.utils.objectPredicate.js

/*
 * Returns a predicate function for use with ko.utils.arrayFirst
 * and similar functions. When comparing the predicate object to
 * the item it first unwraps the item value.
 *
 * Example usage:
 *
 *   ko.utils.arrayFirst(users, objectPredicate({ id: 42 }))
 *
 * or:
 *
 *   ko.utils.arrayFirst(users, objectPredicate('id', 42))
 *
 * When passing in a predicate object you can use multiple keys
 * for comparison:
 *
 *   ko.utils. arrayFirst(users, objectPredicate({ id: 42, email: '[email protected]'}))
 *
 * the `strict` param is automatically shifted to where it makes sense:
 *
 *   objectPredicate({ id: '42' }, true)
 *
 * @param {(string|Object)} predicate           Can be either a key or a predicate object
 * @param {mixed}           value|strict=null   Only used when {predicate} is a string
 * @param {boolean}         strict=false        Compare using == or ===
 *
 * @return {function}                           Returns a matcher function
 */
ko.utils.objectPredicate = function (predicate, value = null, strict = false) {
  if (typeof predicate === 'string') {
    predicate = { [predicate]: value }
  } else if (typeof predicate === 'object') {
    // In case object syntax is used value becomes strict
    strict = value !== null ? value : strict
  } else {
    throw Error('Invalid arguments')
  }

  return function (item) {
    let allTrue = true
    for (let key of Object.keys(predicate)) {
      if (strict) {
        allTrue = allTrue && predicate[key] === ko.unwrap(item[key])
      } else {
        allTrue = allTrue && predicate[key] == ko.unwrap(item[key])
      }
      if (!allTrue) break
    }
    return allTrue
  }
}

Couldn't the predicate checking function be written like:

return function (item) {
    return Object.keys(predicate).every(k => strict ? predicate[k] === ko.unwrap(item[k]) : predicate[k] == ko.unwrap(item[k]));
}

Much better 👍