鑒于 JavaScript 中的這個運算式：
ipad[15] = opad[15] = some[12] = some[13] = undefined
我得到這個 AST（來自 acornjs）：
{
"type": "Program",
"body": [
{
"type": "AssignmentExpression",
"left": {
"type": "MemberExpression",
"object": {
"type": "Identifier",
"start": 3943,
"end": 3947,
"name": "ipad"
},
"property": {
"type": "Literal",
"start": 3948,
"end": 3950,
"value": 15,
"raw": "15"
},
"computed": true
},
"right": {
"type": "AssignmentExpression",
"left": {
"type": "MemberExpression",
"object": {
"type": "Identifier",
"start": 3954,
"end": 3958,
"name": "opad"
},
"property": {
"type": "Literal",
"start": 3959,
"end": 3961,
"value": 15,
"raw": "15"
},
"computed": true
},
"right": {
"type": "AssignmentExpression",
"left": {
"type": "MemberExpression",
"object": {
"type": "Identifier",
"start": 3965,
"end": 3969,
"name": "some"
},
"property": {
"type": "Literal",
"start": 3970,
"end": 3972,
"value": 12,
"raw": "12"
},
"computed": true
},
"right": {
"type": "AssignmentExpression",
"left": {
"type": "MemberExpression",
"object": {
"type": "Identifier",
"start": 3976,
"end": 3980,
"name": "some"
},
"property": {
"type": "Literal",
"start": 3981,
"end": 3983,
"value": 13,
"raw": "13"
},
"computed": true
},
"right": {
"type": "Identifier",
"start": 3987,
"end": 3996,
"name": "undefined"
},
"operator": "="
},
"operator": "="
},
"operator": "="
},
"operator": "="
}
]
}
如何將此 AST 轉換為重新序列化時會產生的內容：
ipad[15] = undefined
opad[15] = undefined
some[12] = undefined
some[13] = undefined
基本上，展平AST。怎么做到呢？我已經考慮了幾個小時并試圖修改此源代碼以使其正常作業，但這有點令人費解。
每個AssignmentExpression都有正確的屬性。所以我覺得只是將它們設定在最頂層到最后一個正確的專案會起作用，但由于某種原因我無法做到。
我正在登錄該normalize_AssignmentExpression功能，它顯示：
RIGHT Node { type: 'Identifier', start: 3987, end: 3996, name: 'undefined' }
RIGHT {
type: 'AssignmentExpression',
left: {
type: 'MemberExpression',
object: Node { type: 'Identifier', start: 3976, end: 3980, name: 'some' },
property: Node {
type: 'Literal',
start: 3981,
end: 3983,
value: 13,
raw: '13'
},
computed: true
},
right: Node {
type: 'Identifier',
start: 3987,
end: 3996,
name: 'undefined'
},
operator: '='
}
RIGHT {
type: 'AssignmentExpression',
left: {
type: 'MemberExpression',
object: Node { type: 'Identifier', start: 3965, end: 3969, name: 'some' },
property: Node {
type: 'Literal',
start: 3970,
end: 3972,
value: 12,
raw: '12'
},
computed: true
},
right: {
type: 'AssignmentExpression',
left: {
type: 'MemberExpression',
object: [Node],
property: [Node],
computed: true
},
right: Node {
type: 'Identifier',
start: 3987,
end: 3996,
name: 'undefined'
},
operator: '='
},
operator: '='
}
RIGHT {
type: 'AssignmentExpression',
left: {
type: 'MemberExpression',
object: Node { type: 'Identifier', start: 3954, end: 3958, name: 'opad' },
property: Node {
type: 'Literal',
start: 3959,
end: 3961,
value: 15,
raw: '15'
},
computed: true
},
right: {
type: 'AssignmentExpression',
left: {
type: 'MemberExpression',
object: [Node],
property: [Node],
computed: true
},
right: {
type: 'AssignmentExpression',
left: [Object],
right: [Node],
operator: '='
},
operator: '='
},
operator: '='
}
不確定這是否有幫助。
我試著讓它像這樣，但它只輸出一個：
function normalize_AssignmentExpression(node, scope) {
const [left, leftExps] = normalizeProperty(node.type, 'left', node.left.type, node.left, scope)
let [right, rightExps] = normalizeProperty(node.type, 'right', node.right.type, node.right, scope)
const exps = [
...leftExps,
...rightExps
]
let furthestRight = right
while (furthestRight.type === 'AssignmentExpression') {
furthestRight = furthestRight.right
}
if (left.type === 'ArrayPattern') {
const assignments = []
left.elements.forEach(el => {
assignments.push(
createAssignmentExpression(
el,
createMemberExpression(right, el),
node.operator
)
)
})
return [
assignments,
exps
]
} else {
console.log('RIGHT', right)
const assignment = createAssignmentExpression(left, furthestRight, node.operator)
return [
assignment,
exps
]
}
}
uj5u.com熱心網友回復：
這樣做：
function normalize_AssignmentExpression(node, scope) {
const [left, leftExps] = normalizeProperty(node.type, 'left', node.left.type, node.left, scope)
let [right, rightExps] = normalizeProperty(node.type, 'right', node.right.type, node.right, scope)
const exps = [
...leftExps,
...rightExps
]
let furthestRight = Array.isArray(right) ? right[0] : right
let rights = Array.isArray(right) ? right.slice(1) : []
let lefts = [left]
while (furthestRight.type === 'AssignmentExpression') {
lefts.push(furthestRight.left)
furthestRight = furthestRight.right
}
if (left.type === 'ArrayPattern') {
const assignments = []
left.elements.forEach(el => {
assignments.push(
createAssignmentExpression(
el,
createMemberExpression(right, el),
node.operator
)
)
})
return [
assignments,
exps
]
} else {
const assignments = []
lefts.forEach(l => {
const assignment = createAssignmentExpression(l, furthestRight, node.operator)
assignments.push(assignment)
})
assignments.push(...rights)
return [
assignments,
exps
]
}
}
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標籤：javascript 算法 抽象语法树
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