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Diffstat (limited to 'node_modules/object.assign/polyfill.js')
-rw-r--r-- | node_modules/object.assign/polyfill.js | 51 |
1 files changed, 51 insertions, 0 deletions
diff --git a/node_modules/object.assign/polyfill.js b/node_modules/object.assign/polyfill.js new file mode 100644 index 000000000..5b6c5774e --- /dev/null +++ b/node_modules/object.assign/polyfill.js @@ -0,0 +1,51 @@ +'use strict'; + +var implementation = require('./implementation'); + +var lacksProperEnumerationOrder = function () { + if (!Object.assign) { + return false; + } + // v8, specifically in node 4.x, has a bug with incorrect property enumeration order + // note: this does not detect the bug unless there's 20 characters + var str = 'abcdefghijklmnopqrst'; + var letters = str.split(''); + var map = {}; + for (var i = 0; i < letters.length; ++i) { + map[letters[i]] = letters[i]; + } + var obj = Object.assign({}, map); + var actual = ''; + for (var k in obj) { + actual += k; + } + return str !== actual; +}; + +var assignHasPendingExceptions = function () { + if (!Object.assign || !Object.preventExtensions) { + return false; + } + // Firefox 37 still has "pending exception" logic in its Object.assign implementation, + // which is 72% slower than our shim, and Firefox 40's native implementation. + var thrower = Object.preventExtensions({ 1: 2 }); + try { + Object.assign(thrower, 'xy'); + } catch (e) { + return thrower[1] === 'y'; + } + return false; +}; + +module.exports = function getPolyfill() { + if (!Object.assign) { + return implementation; + } + if (lacksProperEnumerationOrder()) { + return implementation; + } + if (assignHasPendingExceptions()) { + return implementation; + } + return Object.assign; +}; |