javascript - Get variable name instead of value - Stack Overflow

admin管理员组

文章数量:1026446

Using bash, I think this is possible, but not sure about JavaScript, say we have this:

    const {masterid} = req.query;

    if (!masterid) {
        return res.status(500).send(new Error('Missing query param "masterid".'));
    }

What I want to do is not hardcode "masterid" in the string, instead do something like this:

    const {masterid} = req.query;

    if (!masterid) {
        return res.status(500).send(new Error(`Missing query param "${Reflect(masterid).name()}.".`));
    }

is there a way to do this with the Reflect API?

Using bash, I think this is possible, but not sure about JavaScript, say we have this:

    const {masterid} = req.query;

    if (!masterid) {
        return res.status(500).send(new Error('Missing query param "masterid".'));
    }

What I want to do is not hardcode "masterid" in the string, instead do something like this:

    const {masterid} = req.query;

    if (!masterid) {
        return res.status(500).send(new Error(`Missing query param "${Reflect(masterid).name()}.".`));
    }

is there a way to do this with the Reflect API?

https://developer.mozilla/en-US/docs/Web/JavaScript/Reference/Global_Objects/Reflect

• javascript
• node.js
• reflection

Share Improve this question Follow edited Jul 12, 2021 at 12:56 Machavity♦ 31.7k2727 gold badges9595 silver badges105105 bronze badges asked Sep 17, 2018 at 22:51 Alexander MillsAlexander Mills 101k166166 gold badges539539 silver badges919919 bronze badges 2

• I think the OP is similar to this question: stackoverflow./questions/7861956/… – Alexander Mills Commented Sep 17, 2018 at 22:54
• Not sure exactly what your use case is, but could you use a key/value setup instead? param = { key:"masterid", val="whatever" }. Then if you had a bunch of these you could loop through them and if the value is missing return res.status(500).send(new Error("missing " + iteratedParam.key)) – William Prevett Commented Sep 17, 2018 at 23:03

Add a ment  | 

2 Answers 2

Sorted by: Reset to default 5

From this other post

var masterid = 2;
var text = Object.keys({masterid})[0]; //equals "masterid"

This may be possible for testing/debugging purposes but is inappropriate in production. The only way is to tamper it in some way, e.g. parse it, modify and evaluate. For instance, rewire uses eval to intercept top-level module variables, this approach won't work with scoped variables.

Due to these JavaScript limitations, a proper approach is to not rely on variables. There will be no problems with handling property names. Assertions are mon in Node, this case can make use of helper function:

assertParam(obj, param) {
  assert.ok(obj[param], `Missing param "${param}".`);
}

...

try {
  assertParam(req.query, 'masterid');
} catch (err) {
  return res.status(500).send(err);
}

Using bash, I think this is possible, but not sure about JavaScript, say we have this:

    const {masterid} = req.query;

    if (!masterid) {
        return res.status(500).send(new Error('Missing query param "masterid".'));
    }

What I want to do is not hardcode "masterid" in the string, instead do something like this:

    const {masterid} = req.query;

    if (!masterid) {
        return res.status(500).send(new Error(`Missing query param "${Reflect(masterid).name()}.".`));
    }

is there a way to do this with the Reflect API?

Using bash, I think this is possible, but not sure about JavaScript, say we have this:

    const {masterid} = req.query;

    if (!masterid) {
        return res.status(500).send(new Error('Missing query param "masterid".'));
    }

What I want to do is not hardcode "masterid" in the string, instead do something like this:

    const {masterid} = req.query;

    if (!masterid) {
        return res.status(500).send(new Error(`Missing query param "${Reflect(masterid).name()}.".`));
    }

is there a way to do this with the Reflect API?

https://developer.mozilla/en-US/docs/Web/JavaScript/Reference/Global_Objects/Reflect

• javascript
• node.js
• reflection

Share Improve this question Follow edited Jul 12, 2021 at 12:56 Machavity♦ 31.7k2727 gold badges9595 silver badges105105 bronze badges asked Sep 17, 2018 at 22:51 Alexander MillsAlexander Mills 101k166166 gold badges539539 silver badges919919 bronze badges 2

• I think the OP is similar to this question: stackoverflow./questions/7861956/… – Alexander Mills Commented Sep 17, 2018 at 22:54
• Not sure exactly what your use case is, but could you use a key/value setup instead? param = { key:"masterid", val="whatever" }. Then if you had a bunch of these you could loop through them and if the value is missing return res.status(500).send(new Error("missing " + iteratedParam.key)) – William Prevett Commented Sep 17, 2018 at 23:03

Add a ment  | 

2 Answers 2

Sorted by: Reset to default 5

From this other post

var masterid = 2;
var text = Object.keys({masterid})[0]; //equals "masterid"

This may be possible for testing/debugging purposes but is inappropriate in production. The only way is to tamper it in some way, e.g. parse it, modify and evaluate. For instance, rewire uses eval to intercept top-level module variables, this approach won't work with scoped variables.

Due to these JavaScript limitations, a proper approach is to not rely on variables. There will be no problems with handling property names. Assertions are mon in Node, this case can make use of helper function:

assertParam(obj, param) {
  assert.ok(obj[param], `Missing param "${param}".`);
}

...

try {
  assertParam(req.query, 'masterid');
} catch (err) {
  return res.status(500).send(err);
}

本文标签： javascriptGet variable name instead of valueStack Overflow