Utils

Helper functions that do not belong to any category in particular.

Functions

eRange()

function eRange(start, end?, increment?): Generator<number>;

Defined in: functions/utils.ts:41

Helper function to get an iterator of integers with the specified range, inclusive on the lower end and exclusive on the high end. (The “e” in the function name stands for exclusive.) Thus, this function works in the same way as the built-in range function from Python.

If the end is lower than the start, then an empty range will be returned.

For example:

• eRange(2) returns [0, 1].
• eRange(3) returns [0, 1, 2].
• eRange(-3) returns [0, -1, -2].
• eRange(1, 3) returns [1, 2].
• eRange(2, 5) returns [2, 3, 4].
• eRange(5, 2) returns [].
• eRange(3, 3) returns [].

If you want an array instead of an iterator, use the spread operator like this:

const myArray = [...eRange(1, 3)];

Parameters

Parameter	Type	Default value	Description
start	number	undefined	The integer to start at.
end?	number	undefined	Optional. The integer to end at. If not specified, then the start will be 0 and the first argument will be the end.
increment?	number	1	Optional. The increment to use. Default is 1.

Returns

Generator<number>

---

iRange()

function iRange(start, end?, increment?): Generator<number>;

Defined in: functions/utils.ts:83

Helper function to get an iterator of of integers with the specified range, inclusive on both ends. (The “i” in the function name stands for inclusive.)

If the end is lower than the start, then an empty range will be returned.

For example:

• iRange(2) returns [0, 1, 2].
• iRange(3) returns [0, 1, 2, 3].
• iRange(-3) returns [0, -1, -2, -3].
• iRange(1, 3) returns [1, 2, 3].
• iRange(2, 5) returns [2, 3, 4, 5].
• iRange(5, 2) returns [].
• iRange(3, 3) returns [3].

If you want an array instead of an iterator, use the spread operator like this:

const myArray = [...iRange(1, 3)];

Parameters

Parameter	Type	Default value	Description
start	number	undefined	The integer to start at.
end?	number	undefined	Optional. The integer to end at. If not specified, then the start will be 0 and the first argument will be the end.
increment?	number	1	Optional. The increment to use. Default is 1.

Returns

Generator<number>

---

isKeyOf()

function isKeyOf<T>(key, target): key is keyof T;

Defined in: functions/utils.ts:98

From: https://stackoverflow.com/questions/61526746

Type Parameters

Type Parameter
T extends object

Parameters

Parameter	Type
key	PropertyKey
target	T

Returns

key is keyof T

---

noop()

function noop(): void;

Defined in: functions/utils.ts:110

Helper function to perform a no-op. This can be useful in order to make a trailing return valid in functions that use the early return pattern.

Returns

void

---

parseFloatSafe()

function parseFloatSafe(string): number | undefined;

Defined in: functions/utils.ts:121

This is a more reliable version of Number.parseFloat:

• undefined is returned instead of Number.NaN, which is helpful in conjunction with TypeScript type narrowing patterns.
• Strings that are a mixture of numbers and letters will result in undefined instead of the part of the string that is the number. (e.g., “1a” –> undefined instead of “1a” –> 1)
• Non-strings will result in undefined instead of being coerced to a number.

Parameters

Parameter	Type
string	string

Returns

number | undefined

---

parseIntSafe()

function parseIntSafe(string): number | undefined;

Defined in: functions/utils.ts:151

This is a more reliable version of Number.parseInt:

• undefined is returned instead of Number.NaN, which is helpful in conjunction with TypeScript type narrowing patterns.
• Strings that are a mixture of numbers and letters will result in undefined instead of the part of the string that is the number. (e.g., “1a” –> undefined instead of “1a” –> 1)
• Non-strings will result in undefined instead of being coerced to a number.

If you have to use a radix other than 10, use the vanilla Number.parseInt function instead, because this function ensures that the string contains no letters.

Parameters

Parameter	Type
string	string

Returns

number | undefined

---

repeat()

function repeat(num, func): void;

Defined in: functions/utils.ts:188

Helper function to repeat code N times. This is faster to type and cleaner than using a for loop.

For example:

repeat(10, () => {
  foo();
});

The repeated function is passed the index of the iteration, if needed:

repeat(3, (i) => {
  console.log(i); // Prints "0", "1", "2"
});

Parameters

Parameter	Type
num	number
func	(i) => void

Returns

void

---

todo()

function todo(...args): void;

Defined in: functions/utils.ts:210

Helper function to signify that the enclosing code block is not yet complete. Using this function is similar to writing a “TODO” comment, but it has the benefit of preventing ESLint errors due to unused variables or early returns.

When you see this function, it simply means that the programmer intends to add in more code to this spot later.

This function is variadic, meaning that you can pass as many arguments as you want. (This is useful as a means to prevent unused variables.)

This function does not actually do anything. (It is an “empty” function.)

Parameters

Parameter	Type
…args	readonly unknown[]

Returns

void

Allow Empty Variadic