Strict mode Passingnon-Strict mode Passing
Features:
- Symbol.toPrimitive
// Copyright (C) 2016 the V8 project authors. All rights reserved. // This code is governed by the BSD license found in the LICENSE file. /*--- esid: sec-addition-operator-plus-runtime-semantics-evaluation es6id: 12.7.3.1 description: > Behavior when coercion via `Symbol.toPrimitive` yields a primitive value info: | [...] 5. Let lprim be ? ToPrimitive(lval). 6. Let rprim be ? ToPrimitive(rval). 7. If Type(lprim) is String or Type(rprim) is String, then a. Let lstr be ? ToString(lprim). b. Let rstr be ? ToString(rprim). c. Return the String that is the result of concatenating lstr and rstr. 8. Let lnum be ? ToNumber(lprim). 9. Let rnum be ? ToNumber(rprim). 10. Return the result of applying the addition operation to lnum and rnum. See the Note below 12.8.5. ES6 Section 7.1.1 ToPrimitive ( input [, PreferredType] ) [...] 4. Let exoticToPrim be GetMethod(input, @@toPrimitive). 5. ReturnIfAbrupt(exoticToPrim). 6. If exoticToPrim is not undefined, then a. Let result be Call(exoticToPrim, input, «hint»). b. ReturnIfAbrupt(result). c. If Type(result) is not Object, return result. features: [Symbol.toPrimitive] ---*/ var y = {}; var retVal; y[Symbol.toPrimitive] = function() { return retVal; }; retVal = 86; assert.sameValue(1 + y, 87); assert.sameValue(y + 2, 88); assert.sameValue('s' + y, 's86'); assert.sameValue(y + 's', '86s'); retVal = 'str'; assert.sameValue(0 + y, '0str'); assert.sameValue(y + 0, 'str0'); assert.sameValue('s' + y, 'sstr'); assert.sameValue(y + 's', 'strs'); retVal = Symbol.toPrimitive; assert.throws(TypeError, function() { 0 + y; }, 'ToNumber(Symbol): right-hand side'); assert.throws(TypeError, function() { y + 0; }, 'ToNumber(Symbol): left-hand side'); assert.throws(TypeError, function() { '' + y; }, 'ToString(Symbol): right-hand side'); assert.throws(TypeError, function() { y + ''; }, 'ToString(Symbol): left-hand size');