value-or-function

Normalize a value or function, applying extra args to the function

Example

var normalize = require('value-or-function');

// Values matching type are returned
var isEnabled = normalize('boolean', true);
// isEnabled === true

// Values not matching type return undefined
var isEnabled = normalize('boolean', 1);
// isEnabled === undefined

// Functions are called
var isEnabled = normalize('boolean', function() {
  return false;
});
// isEnabled === false

// Extra arguments are applied to function
var count = normalize('number', function(a, b) {
  return a + b;
}, 1, 2);
// count === 3

// Supply the function with context
var context = { c: 3 };
var count = normalize.call(context, 'number', function(a, b) {
  return a + b + this.c;
}, 1, 2);
// count === 6

// Values one of multiple types are returned
var isEnabled = normalize(['string', 'boolean'], true);
// isEnabled === true

// Provide a function as first argument to do custom coercion
var now = new Date();
var enabledSince = normalize(function(value) {
  if (value.constructor === Date) {
    return value;
  }
}, now);
// enabledSince === now

// Convenience methods are available for the built-in types
var result = normalize.object({});
var result = normalize.number(1);
var result = normalize.string('');
var result = normalize.symbol(Symbol());
var result = normalize.boolean(true);
var result = normalize.function(function() {});
var result = normalize.date(new Date());

API

normalize(coercer, value[, ...appliedArguments])

Takes a coercer function coercer to transform value to the desired type. Also optionally takes any extra arguments to apply to value if value is a function.

If the return value of coercer(value) is not null or undefined, that value is returned. Otherwise, if value is a function, that function is called with any extra arguments supplied to normalize, and its return value is passed through the coercer.

If coercer is a string, it must be one of the built-in types (see below) and the appropriate default coercer is invoked, optionally first reducing value to a primitive type with .valueOf() if it is an Object.

If coercer is an array, each element is tried until one returns something other than null or undefined, or it results in undefined if all of the elements yield null or undefined.

normalize.object(value[, ...appliedArguments])

Convenience method for normalize('object', ...).

normalize.number(value[, ...appliedArguments])

Convenience method for normalize('number', ...).

normalize.string(value[, ...appliedArguments])

Convenience method for normalize('string', ...).

normalize.symbol(value[, ...appliedArguments])

Convenience method for normalize('symbol', ...).

normalize.boolean(value[, ...appliedArguments])

Convenience method for normalize('boolean', ...).

normalize.function(value[, ...appliedArguments])

Convenience method for normalize('function', ...).

normalize.date(value[, ...appliedArguments])

Convenience method for normalize('date', ...).

License

MIT