index.js
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'use strict';
var test = require('tape');
var isSymbol = require('../index');
var forEach = function (arr, func) {
var i;
for (i = 0; i < arr.length; ++i) {
func(arr[i], i, arr);
}
};
var hasSymbols = typeof Symbol === 'function' && typeof Symbol() === 'symbol';
var debug = function (value, msg) {
var output = '';
if (hasSymbols) {
try { output += String(value); }
catch (e) { output += Symbol.prototype.toString.call(value); }
if (output === '') {
output = JSON.stringify(value);
}
}
var type = Object.prototype.toString.call(value).toLowerCase().slice(8, -1);
output += ' (' + type;
var typeOf = typeof value;
if (type !== typeOf) {
output += ', typeof: ' + typeOf;
}
return output + ') ' + msg;
};
test('non-symbol values', function (t) {
var nonSymbols = [
true,
false,
Object(true),
Object(false),
null,
undefined,
{},
[],
/a/g,
'string',
42,
new Date(),
function () {},
NaN
];
t.plan(nonSymbols.length);
forEach(nonSymbols, function (nonSymbol) {
t.equal(false, isSymbol(nonSymbol), debug(nonSymbol, 'is not a symbol'));
});
t.end();
});
test('faked symbol values', function (t) {
t.test('real symbol valueOf', { skip: !hasSymbols }, function (st) {
var fakeSymbol = { valueOf: function () { return Symbol('foo'); } };
st.equal(false, isSymbol(fakeSymbol), 'object with valueOf returning a symbol is not a symbol');
st.end();
});
t.test('faked @@toStringTag', { skip: !hasSymbols || !Symbol.toStringTag }, function (st) {
var fakeSymbol = { valueOf: function () { return Symbol('foo'); } };
fakeSymbol[Symbol.toStringTag] = 'Symbol';
st.equal(false, isSymbol(fakeSymbol), 'object with fake Symbol @@toStringTag and valueOf returning a symbol is not a symbol');
var notSoFakeSymbol = { valueOf: function () { return 42; } };
notSoFakeSymbol[Symbol.toStringTag] = 'Symbol';
st.equal(false, isSymbol(notSoFakeSymbol), 'object with fake Symbol @@toStringTag and valueOf not returning a symbol is not a symbol');
st.end();
});
var fakeSymbolString = { toString: function () { return 'Symbol(foo)'; } };
t.equal(false, isSymbol(fakeSymbolString), 'object with toString returning Symbol(foo) is not a symbol');
t.end();
});
test('Symbol support', { skip: !hasSymbols }, function (t) {
t.test('well-known Symbols', function (st) {
var wellKnownSymbols = Object.getOwnPropertyNames(Symbol).filter(function filterer(name) {
return name !== 'for' && name !== 'keyFor' && !(name in filterer);
});
wellKnownSymbols.forEach(function (name) {
var sym = Symbol[name];
st.equal(true, isSymbol(sym), debug(sym, ' is a symbol'));
});
st.end();
});
t.test('user-created symbols', function (st) {
var symbols = [
Symbol(),
Symbol('foo'),
Symbol.for('foo'),
Object(Symbol('object'))
];
symbols.forEach(function (sym) {
st.equal(true, isSymbol(sym), debug(sym, ' is a symbol'));
});
st.end();
});
t.end();
});