[英]add in the middle of a pipe stream node js
I'm currently building a scheduling application in nodeJS. 我目前正在nodeJS中构建调度应用程序。
I have a template of a schedule that i'd like to generate dynamically. 我有一个时间表的模板,我想动态生成。 I know this is possible with stream, more specifically with pipes although I'm unable to get it to inject code in the middle of the stream.
我知道这在流中是可能的,更具体地说是在管道中,尽管我无法使其在流中注入代码。
What I've tried: 我尝试过的
var through2 = require( "through2" );
input.pipe(through2(function (chunk, encoding, done){
var transformChunk = chunk.toString()
console.log(transformChunk);
if (transformChunk.includes("\\newDay{}{}")){
transformChunk += "newDay{12}{12}";
this.push(transformChunk);
}
done();
}))
this simply doesn't change anything. 这根本不会改变任何东西。
I've also tried to make my own custom transform class 我也尝试制作自己的自定义转换类
const { Transform } = require('stream');
class injectText extends Transform {
constructor(string){
super();
this.replaceString = string;
}
_transform(chunk, encoding, callback) {
// var transformChunk = chunk.toString().replace("newDay{}{}", this.replaceString);
var transformChunk = chunk.toString()
if (transformChunk.includes("newDay{}{}")){
transformChunk += "newDay{12}{12}";
}
this.push(transformChunk)
console.log(transformChunk);
callback();
}
};
var changedStream = new injectText('newDay{11}{11}');
but this only adds to the end of the steam. 但这只会增加蒸汽的消耗。
String replace works only for one line. 字符串替换仅适用于一行。
My issue is that I need to replace that one line with multiple new lines. 我的问题是我需要用多行新行替换这一行。
Is it possible to use async generator ( async *function
) and async iterator ( for await
) for this? 是否可以为此使用异步生成器(
async *function
)和异步迭代器( for await
)? It would be roughly like this: 大概是这样的:
async *inputGenerator() {
for await (const chunk of input) {
var transformedChunk = chunk.toString();
if (transformedChunk.includes("\\newDay{}{}")){
transformedChunk += "newDay{12}{12}";
}
yield transformedChunk;
}
}
// do something with the transformed input
for await (const chunk of inputGenerator()) {
.....
}
Async iterators are available on ES2018/Node 10 异步迭代器在ES2018 / Node 10上可用
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