polyfill-service
Version:
A polyfill combinator
150 lines (133 loc) • 7.62 kB
JavaScript
// https://github.com/es-shims/es5-shim/blob/d6d7ff1b131c7ba14c798cafc598bb6780d37d3b/es5-shim.js#L182
Object.defineProperty(Function.prototype, 'bind', {
value: function bind(that) { // .length is 1
// add necessary es5-shim utilities
var $Array = Array;
var $Object = Object;
var ObjectPrototype = $Object.prototype;
var ArrayPrototype = $Array.prototype;
var Empty = function Empty() {};
var to_string = ObjectPrototype.toString;
var hasToStringTag = typeof Symbol === 'function' && typeof Symbol.toStringTag === 'symbol';
var isCallable; /* inlined from https://npmjs.com/is-callable */ var fnToStr = Function.prototype.toString, tryFunctionObject = function tryFunctionObject(value) { try { fnToStr.call(value); return true; } catch (e) { return false; } }, fnClass = '[object Function]', genClass = '[object GeneratorFunction]'; isCallable = function isCallable(value) { if (typeof value !== 'function') { return false; } if (hasToStringTag) { return tryFunctionObject(value); } var strClass = to_string.call(value); return strClass === fnClass || strClass === genClass; };
var array_slice = ArrayPrototype.slice;
var array_concat = ArrayPrototype.concat;
var array_push = ArrayPrototype.push;
var max = Math.max;
// /add necessary es5-shim utilities
// 1. Let Target be the this value.
var target = this;
// 2. If IsCallable(Target) is false, throw a TypeError exception.
if (!isCallable(target)) {
throw new TypeError('Function.prototype.bind called on incompatible ' + target);
}
// 3. Let A be a new (possibly empty) internal list of all of the
// argument values provided after thisArg (arg1, arg2 etc), in order.
// XXX slicedArgs will stand in for "A" if used
var args = array_slice.call(arguments, 1); // for normal call
// 4. Let F be a new native ECMAScript object.
// 11. Set the [[Prototype]] internal property of F to the standard
// built-in Function prototype object as specified in 15.3.3.1.
// 12. Set the [[Call]] internal property of F as described in
// 15.3.4.5.1.
// 13. Set the [[Construct]] internal property of F as described in
// 15.3.4.5.2.
// 14. Set the [[HasInstance]] internal property of F as described in
// 15.3.4.5.3.
var bound;
var binder = function () {
if (this instanceof bound) {
// 15.3.4.5.2 [[Construct]]
// When the [[Construct]] internal method of a function object,
// F that was created using the bind function is called with a
// list of arguments ExtraArgs, the following steps are taken:
// 1. Let target be the value of F's [[TargetFunction]]
// internal property.
// 2. If target has no [[Construct]] internal method, a
// TypeError exception is thrown.
// 3. Let boundArgs be the value of F's [[BoundArgs]] internal
// property.
// 4. Let args be a new list containing the same values as the
// list boundArgs in the same order followed by the same
// values as the list ExtraArgs in the same order.
// 5. Return the result of calling the [[Construct]] internal
// method of target providing args as the arguments.
var result = target.apply(
this,
array_concat.call(args, array_slice.call(arguments))
);
if ($Object(result) === result) {
return result;
}
return this;
} else {
// 15.3.4.5.1 [[Call]]
// When the [[Call]] internal method of a function object, F,
// which was created using the bind function is called with a
// this value and a list of arguments ExtraArgs, the following
// steps are taken:
// 1. Let boundArgs be the value of F's [[BoundArgs]] internal
// property.
// 2. Let boundThis be the value of F's [[BoundThis]] internal
// property.
// 3. Let target be the value of F's [[TargetFunction]] internal
// property.
// 4. Let args be a new list containing the same values as the
// list boundArgs in the same order followed by the same
// values as the list ExtraArgs in the same order.
// 5. Return the result of calling the [[Call]] internal method
// of target providing boundThis as the this value and
// providing args as the arguments.
// equiv: target.call(this, ...boundArgs, ...args)
return target.apply(
that,
array_concat.call(args, array_slice.call(arguments))
);
}
};
// 15. If the [[Class]] internal property of Target is "Function", then
// a. Let L be the length property of Target minus the length of A.
// b. Set the length own property of F to either 0 or L, whichever is
// larger.
// 16. Else set the length own property of F to 0.
var boundLength = max(0, target.length - args.length);
// 17. Set the attributes of the length own property of F to the values
// specified in 15.3.5.1.
var boundArgs = [];
for (var i = 0; i < boundLength; i++) {
array_push.call(boundArgs, '$' + i);
}
// XXX Build a dynamic function with desired amount of arguments is the only
// way to set the length property of a function.
// In environments where Content Security Policies enabled (Chrome extensions,
// for ex.) all use of eval or Function costructor throws an exception.
// However in all of these environments Function.prototype.bind exists
// and so this code will never be executed.
bound = Function('binder', 'return function (' + boundArgs.join(',') + '){ return binder.apply(this, arguments); }')(binder);
if (target.prototype) {
Empty.prototype = target.prototype;
bound.prototype = new Empty();
// Clean up dangling references.
Empty.prototype = null;
}
// TODO
// 18. Set the [[Extensible]] internal property of F to true.
// TODO
// 19. Let thrower be the [[ThrowTypeError]] function Object (13.2.3).
// 20. Call the [[DefineOwnProperty]] internal method of F with
// arguments "caller", PropertyDescriptor {[[Get]]: thrower, [[Set]]:
// thrower, [[Enumerable]]: false, [[Configurable]]: false}, and
// false.
// 21. Call the [[DefineOwnProperty]] internal method of F with
// arguments "arguments", PropertyDescriptor {[[Get]]: thrower,
// [[Set]]: thrower, [[Enumerable]]: false, [[Configurable]]: false},
// and false.
// TODO
// NOTE Function objects created using Function.prototype.bind do not
// have a prototype property or the [[Code]], [[FormalParameters]], and
// [[Scope]] internal properties.
// XXX can't delete prototype in pure-js.
// 22. Return F.
return bound;
}
});