扩展JavaScript语法以添加键入

Question

我想扩展JavaScript以添加自定义类型检查。

，例如

function test(welcome:string, num:integer:non-zero) {
   console.log(welcome + num)
}

将编译为：

function test(welcome, num) {
    if(Object.prototype.toString.call(welcome) !== "[object String]") {
        throw new Error('welcome must be a string')
    }
    if (!Number.isInteger(num)) {
        throw new Error('num must be an integer')
    }
    console.log(welcome + num)
}

这样做的最直接方法是什么？

到目前为止，我已经看过：

• sweet.js(在线文档看起来过时了，因为我认为它正在经历某种内部重写(
• Esprima和Escodegen(不确定从哪里开始(
• 使用常规表达子手动解析

Answer 1

在评估所有各种选项后，使用sweet.js似乎是最好的解决方案。开始工作仍然很难(我可能以错误的方式做事(，但以防万一某人想在这里做类似的事情是我的解决方案。

    'use strict'
    syntax function = function(ctx) {
        let funcName   = ctx.next().value;
        let funcParams = ctx.next().value;
        let funcBody   = ctx.next().value;
        //produce the normal params array
        var normalParams = produceNormalParams(funcParams)
        //produce the checks
        var paramChecks = produceParamChecks(funcParams)
        //produce the original funcBody code
        //put them together as the final result
        var params = ctx.contextify(funcParams)
        var paramsArray = []
        for (let stx of params) {
            paramsArray.push(stx)
        }
        var inner = #``
        var innerStuff = ctx.contextify(funcBody)
        for (let item of innerStuff) {
            inner = inner.concat(#`${item}`)
        }
        var result = #`function ${funcName} ${normalParams} {
            ${paramChecks}
            ${inner}
        }`
        return result
        function extractParamsAndParamChecks(paramsToken) {
            var paramsContext = ctx.contextify(paramsToken)
            //extracts the actual parameters
            var paramsArray = []
            var i = 0;
            var firstItembyComma = true
            for (let paramItem of paramsContext) {
                if (firstItembyComma) {
                    paramsArray.push({
                        param: paramItem,
                        checks: []
                    })
                    firstItembyComma = false
                }
                if (paramItem.value.token.value === ',') {
                    firstItembyComma = true
                    i++
                } else {
                    paramsArray[i].checks.push(paramItem.value.token.value)
                }
            }
            for (var i = 0; i < paramsArray.length; i++) {
                var checks = paramsArray[i].checks.join('').split(':')
                checks.splice(0, 1)
                paramsArray[i].checks = checks
            }
            return paramsArray
        }
        function produceNormalParams(paramsToken) {
            var paramsArray = extractParamsAndParamChecks(paramsToken)
            //Produces the final params #string
            var inner = #``
            var first = true
            for (let item of paramsArray) {
                if (first === true) {
                    inner = inner.concat(#`${item.param}`)
                } else {
                    inner = inner.concat(#`,${item.param}`)
                }
            }
            return #`(${inner})`
        }
        function produceParamChecks(paramsToken) {
            var paramsArray = extractParamsAndParamChecks(paramsToken)
            var result = #``
            for (let paramObject of paramsArray) {
                var tests = produceChecks(paramObject)
                result = result.concat(#`${tests}`)
            }
            return result
        }
        function produceChecks(paramObject) {
            var paramToken = paramObject.param
            var itemType   = paramObject.checks[0]
            var checks     = paramObject.checks
            if (itemType === undefined) return #``
            if (itemType === 'array') {
                return #`if (Object.prototype.toString.call(${paramToken}) !== "[object Array]") throw new Error('Must be array:' + ${paramToken})`
             else {
                throw new Error('item type not recognised: ' + itemType)
            }
        }
    }