如何知道函数被调用时是否是 await 调用?
发布于 12 天前 作者 ahuangege 1271 次浏览 来自 问答
async function test2() {
    test();
    await test();
}

function test() {
    // I want to know if this is called by await ...
}
6 回复

普通解法

var _original=window.alert;
window.alert=function(){
    console.log('in');
    var result=_original.apply(this,arguments);
    console.log('out');
    return result;
}

new Error().stack

看调用栈吧

具体特征取决于你的代码构建后的结果, 例如 ts

var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
    return new (P || (P = Promise))(function (resolve, reject) {
        function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
        function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
        step((generator = generator.apply(thisArg, _arguments || [])).next());
    });
};
var __generator = (this && this.__generator) || function (thisArg, body) {
    var _ = { label: 0, sent: function() { if (t[0] & 1) throw t[1]; return t[1]; }, trys: [], ops: [] }, f, y, t, g;
    return g = { next: verb(0), "throw": verb(1), "return": verb(2) }, typeof Symbol === "function" && (g[Symbol.iterator] = function() { return this; }), g;
    function verb(n) { return function (v) { return step([n, v]); }; }
    function step(op) {
        if (f) throw new TypeError("Generator is already executing.");
        while (_) try {
            if (f = 1, y && (t = op[0] & 2 ? y["return"] : op[0] ? y["throw"] || ((t = y["return"]) && t.call(y), 0) : y.next) && !(t = t.call(y, op[1])).done) return t;
            if (y = 0, t) op = [op[0] & 2, t.value];
            switch (op[0]) {
                case 0: case 1: t = op; break;
                case 4: _.label++; return { value: op[1], done: false };
                case 5: _.label++; y = op[1]; op = [0]; continue;
                case 7: op = _.ops.pop(); _.trys.pop(); continue;
                default:
                    if (!(t = _.trys, t = t.length > 0 && t[t.length - 1]) && (op[0] === 6 || op[0] === 2)) { _ = 0; continue; }
                    if (op[0] === 3 && (!t || (op[1] > t[0] && op[1] < t[3]))) { _.label = op[1]; break; }
                    if (op[0] === 6 && _.label < t[1]) { _.label = t[1]; t = op; break; }
                    if (t && _.label < t[2]) { _.label = t[2]; _.ops.push(op); break; }
                    if (t[2]) _.ops.pop();
                    _.trys.pop(); continue;
            }
            op = body.call(thisArg, _);     // 始终从这里进入test2的主体, 调用栈顶部附近应该有名为 step 的函数调用
        } catch (e) { op = [6, e]; y = 0; } finally { f = t = 0; }
        if (op[0] & 5) throw op[1]; return { value: op[0] ? op[1] : void 0, done: true };
    }
};
function test2() {
    return __awaiter(this, void 0, void 0, function () {
        return __generator(this, function (_a) {
            switch (_a.label) {
                case 0:
                    test();
                    return [4 /*yield*/, test()];  // test() 的执行时机, 会发现其会在 "yield"(实际为return) 之前调用
                case 1:
                    _a.sent();
                    return [2 /*return*/];
            }
        });
    });
}
function test() {
    // I want to know if this is called by await ...
}

如果原生支持 await, 没想到啥办法, 可能需要arguments.caller这类黑魔法

可以了解一下 zone.js

async function test2() {
    const ret = test();
	if (ret instanceof Promise)
    	await ret;
}
// 或者
async function test2() {
    await test(); //非异步结果也可以await
}
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