| [ArrayMapper](./js-utils.arraymapper.md) | Map an array of items into a map of arrays using the specified keys, able to <code>skip</code> initial items and gather remaining items into a <code>rest</code> key. |
| [concat(chunks)](./js-utils.concat.md) | Concatenate a list of buffers. |
| [constructorName(val)](./js-utils.constructorname.md) | Get the constructor name from an instance. |
| [defaultWhen(condition, items)](./js-utils.defaultwhen.md) | Return the first element when <code>condition</code> is true and the second element when <code>condition</code> is false. |
| [deferUntil(cb, step, max)](./js-utils.deferuntil.md) | Resolve if <code>cb</code> returns true within <code>max</code> tries, otherwise reject with a <code>TimeoutError</code>. |
| [deferValue(ms, val)](./js-utils.defervalue.md) | Resolve with the given value, after a set amount of time. |
| [filterZip(cb, l1)](./js-utils.filterzip.md) | Filter and zip some arrays. The <code>cb</code> is called for each slice, which is kept if <code>cb</code> returns true. |
| [getHead(map, key)](./js-utils.gethead.md) | Get the first element from the specified key within a map of lists. |
| [getHeadOrDefault(map, key, defaultValue)](./js-utils.getheadordefault.md) | Get the first element from the specified key, within a map of lists, or a default value when the key does not exist or is nil. |
| [getTestLogger(verbose)](./js-utils.gettestlogger.md) | Get a test logger. Returns a null logger unless <code>verbose</code> is true or run under debug mode. |
| [hasItems(val)](./js-utils.hasitems.md) | Test if a value is an array with some items (<code>length > 0</code>).<!-- -->This is not a general replacement for <code>.length > 0</code>, since it is also a typeguard: <code>if (hasItems(val)) else { val }</code> will complain that <code>val</code> is <code>never</code> in the <code>else</code> branch, since it was proven not to be an array by this function, even if <code>val</code> is simply empty. |
| [isEmpty(val)](./js-utils.isempty.md) | Check if a <code>Maybe<Array<T>></code> does in fact contain an array, and that array has items. |
| [isNone(val)](./js-utils.isnone.md) | Typeguard to check if a <code>Maybe</code> is <code>None</code> (null or undefined). |
| [isSome(val)](./js-utils.issome.md) | Typeguard to check if a <code>Maybe</code> is <code>Some</code> value (not <code>None</code>). |
| [leftPad(val, min, fill)](./js-utils.leftpad.md) | Prefix <code>val</code> with <code>fill</code> until it is at least <code>min</code> characters. |
| [lengthOf(val)](./js-utils.lengthof.md) | Calculate the length of an array or value.<!-- -->Arrays return their length, single values return 1, and nil values return 0. This counts the number of elements that setOrPush would add. |
| [mergeMap(target, source)](./js-utils.mergemap.md) | Merge the <code>source</code> map into the <code>target</code> map, replacing keys that already exist. |
| [mustCoalesce(values)](./js-utils.mustcoalesce.md) | Return the first value that is not nil. |
| [mustDefault(values)](./js-utils.mustdefault.md) | Return the first value that is some <code>T</code>. Throw if they are all <code>None</code>. |
| [mustExist(val, err)](./js-utils.mustexist.md) | Assert that a variable is not <code>None</code> and return the value. Throw if it is <code>None</code>. |
| [spyLogger(spies)](./js-utils.spylogger.md) | Create a spy logger using the provided methods, which returns itself as a child. ensure all methods are present by extending null logger |
| [toArray(val)](./js-utils.toarray_1.md) | Copy an existing readonly array-like or convert a single value to a readonly array. |
| [trim(val, max, tail)](./js-utils.trim.md) | Return the start of <code>val</code>, up to <code>max</code> characters. If <code>val</code> is longer than <code>max</code> and there is room, suffix with <code>tail</code>. |
