Node.js中For循环中的async.waterfall [英] async.waterfall in a For Loop in Node.js
本文介绍了Node.js中For循环中的async.waterfall的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
在 async.waterfall
中使用对于循环,似乎
for
循环在嵌套的 async.waterfall之前迭代
完成所有步骤。如何避免这种情况?
When using async.waterfall
within a for
loop, it appears that the for
loop iterates before the nested async.waterfall
finishes all its steps. How can this be avoided?
for(var i = 0; i < users.length; i++ ) {
console.log(i)
async.waterfall([
function(callback) {
callback(null, 'one', 'two');
},
function(arg1, arg2, callback) {
// arg1 now equals 'one' and arg2 now equals 'two'
callback(null, 'three');
},
function(arg1, callback) {
// arg1 now equals 'three'
callback(null, 'done');
}
], function (err, result) {
// result now equals 'done'
console.log('done')
});
}
输出
0
1
2
3
4
done
done
done
done
done
期望输出
0
done
1
done
2
done
3
done
4
done
推荐答案
你可以像这样使用async的forEachLimit
You can use like this with async's forEachLimit
var async = require("async")
var users = []; // Initialize user array or get it from DB
async.forEachLimit(users, 1, function(user, userCallback){
async.waterfall([
function(callback) {
callback(null, 'one', 'two');
},
function(arg1, arg2, callback) {
// arg1 now equals 'one' and arg2 now equals 'two'
callback(null, 'three');
},
function(arg1, callback) {
// arg1 now equals 'three'
callback(null, 'done');
}
], function (err, result) {
// result now equals 'done'
console.log('done')
userCallback();
});
}, function(err){
console.log("User For Loop Completed");
});
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