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ruanyf 2015-11-12 19:42:07 +08:00
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@ -34,7 +34,7 @@ ECMAScript 6规格的26章之中第1章到第3章是对文件本身的介绍
规格对每一种语法行为的描述,都分成两部分:先是总体的行为描述,然后是实现的算法细节。相等运算符的总体描述,只有一句话。
> “The comparison `x == y`, where x and y are values, produces `true` or `false`.”
> “The comparison `x == y`, where `x` and `y` are values, produces `true` or `false`.”
上面这句话的意思是,相等运算符用于比较两个值,返回`true``false`
@ -42,21 +42,21 @@ ECMAScript 6规格的26章之中第1章到第3章是对文件本身的介绍
> 1. ReturnIfAbrupt(x).
> 1. ReturnIfAbrupt(y).
> 1. If Type(x) is the same as Type(y), then
> Return the result of performing Strict Equality Comparison x === y.
> 1. If x is null and y is undefined, return true.
> 1. If x is undefined and y is null, return true.
> 1. If Type(x) is Number and Type(y) is String,
> return the result of the comparison x == ToNumber(y).
> 1. If Type(x) is String and Type(y) is Number,
> 1. If `Type(x)` is the same as `Type(y)`, then
> Return the result of performing Strict Equality Comparison `x === y`.
> 1. If `x` is `null` and `y` is `undefined`, return `true`.
> 1. If `x` is `undefined` and `y` is `null`, return `true`.
> 1. If `Type(x)` is Number and `Type(y)` is String,
> return the result of the comparison `x == ToNumber(y)`.
> 1. If `Type(x)` is String and `Type(y)` is Number,
> return the result of the comparison ToNumber(x) == y.
> 1. If Type(x) is Boolean, return the result of the comparison ToNumber(x) == y.
> 1. If Type(y) is Boolean, return the result of the comparison x == ToNumber(y).
> 1. If Type(x) is either String, Number, or Symbol and Type(y) is Object, then
> return the result of the comparison x == ToPrimitive(y).
> 1. If Type(x) is Object and Type(y) is either String, Number, or Symbol, then
> return the result of the comparison ToPrimitive(x) == y.
> 1. Return false.
> 1. If `Type(x)` is Boolean, return the result of the comparison `ToNumber(x) == y`.
> 1. If `Type(y)` is Boolean, return the result of the comparison `x == ToNumber(y)`.
> 1. If `Type(x)` is either String, Number, or Symbol and `Type(y)` is Object, then
> return the result of the comparison `x == ToPrimitive(y)`.
> 1. If `Type(x)` is Object and `Type(y)` is either String, Number, or Symbol, then
> return the result of the comparison `ToPrimitive(x) == y`.
> 1. Return `false`.
上面这段算法一共有12步翻译如下。
@ -138,7 +138,7 @@ a2.map(n => 1) // [, , ,]
后面的算法描述是这样的。
> 1. Let O be ToObject(this value).
> 1. Let `O` be `ToObject(this value)`.
> 1. ReturnIfAbrupt(O).
> 1. Let len be ToLength(Get(O, "length")).
> 1. ReturnIfAbrupt(len).
@ -147,17 +147,17 @@ a2.map(n => 1) // [, , ,]
> 1. Let A be ArraySpeciesCreate(O, len).
> 1. ReturnIfAbrupt(A).
> 1. Let k be 0.
> 1. Repeat, while k < len
> a. Let Pk be ToString(k).
> b. Let kPresent be HasProperty(O, Pk).
> c. ReturnIfAbrupt(kPresent).
> d. If kPresent is true, then
> d-1. Let kValue be Get(O, Pk).
> d-2. ReturnIfAbrupt(kValue).
> d-3. Let mappedValue be Call(callbackfn, T, «kValue, k, O»).
> d-4. ReturnIfAbrupt(mappedValue).
> d-5. Let status be CreateDataPropertyOrThrow (A, Pk, mappedValue).
> d-6. ReturnIfAbrupt(status).
> 1. Repeat, while k < len
> a. Let Pk be ToString(k).
> b. Let kPresent be HasProperty(O, Pk).
> c. ReturnIfAbrupt(kPresent).
> d. If kPresent is true, then
> d-1. Let kValue be Get(O, Pk).
> d-2. ReturnIfAbrupt(kValue).
> d-3. Let mappedValue be Call(callbackfn, T, «kValue, k, O»).
> d-4. ReturnIfAbrupt(mappedValue).
> d-5. Let status be CreateDataPropertyOrThrow (A, Pk, mappedValue).
> d-6. ReturnIfAbrupt(status).
> e. Increase k by 1.
> 1. Return A.
@ -172,17 +172,17 @@ a2.map(n => 1) // [, , ,]
> 1. 生成一个新的数组`A`,跟当前数组的`length`属性保持一致
> 1. 如果报错就返回
> 1. 设定`k`等于0
> 1. 只要`k`小于当前数组的`length`属性,就重复下面步骤
> a. 设定`Pk`等于`ToString(k)`,即将`K`转为字符串
> b. 设定`kPresent`等于`HasProperty(O, Pk)`,即求当前数组有没有指定属性
> c. 如果报错就返回
> d. 如果`kPresent`等于`true`,则进行下面步骤
> d-1. 设定`kValue`等于`Get(O, Pk)`,取出当前数组的指定属性
> d-2. 如果报错就返回
> d-3. 设定`mappedValue`等于`Call(callbackfn, T, «kValue, k, O»)`,即执行回调函数
> d-4. 如果报错就返回
> d-5. 设定`status`等于`CreateDataPropertyOrThrow (A, Pk, mappedValue)`,即将回调函数的值放入`A`数组的指定位置
> d-6. 如果报错就返回
> 1. 只要`k`小于当前数组的`length`属性,就重复下面步骤
> a. 设定`Pk`等于`ToString(k)`,即将`K`转为字符串
> b. 设定`kPresent`等于`HasProperty(O, Pk)`,即求当前数组有没有指定属性
> c. 如果报错就返回
> d. 如果`kPresent`等于`true`,则进行下面步骤
> d-1. 设定`kValue`等于`Get(O, Pk)`,取出当前数组的指定属性
> d-2. 如果报错就返回
> d-3. 设定`mappedValue`等于`Call(callbackfn, T, «kValue, k, O»)`,即执行回调函数
> d-4. 如果报错就返回
> d-5. 设定`status`等于`CreateDataPropertyOrThrow (A, Pk, mappedValue)`,即将回调函数的值放入`A`数组的指定位置
> d-6. 如果报错就返回
> e. `k`增加1
> 1. 返回`A`