How to convert a javascript object array file to customized json file

Question

I'm getting a javascript object array. I'm trying to write it to json file by replacing certain params. i don't require comma separated between every object and need to insert a new json object before every existing object. current js object is

[{name:"abc", age:22},
 {name:"xyz", age:32,
 {name:"lmn", age:23}]

the expected json output file is,

{"index":{}}
{name:"abc", age:22}
{"index":{}}
{name:"xyz", age:32}
{"index":{}}
{name:"lmn", age:23}

My code is

sourceData = data.map((key) => key['_source'])
const strData = JSON.stringify(sourceData);
const newStr = strData.replace("},{", "}\n{");
const newStr2 = newStr.replace(`{"name"`, `{"index" : {}}\n{"name"`);
fs.writeFile('data.json', newStr2, (err) => {
    if (err) {
        throw err;
    }
    console.log("JSON data is saved.");
});

But in my output only the first object is changing. I need this to happen my entire output json file. Please help. Thanks

georg · Accepted Answer · 2021-04-21 11:36:48Z

2

I'd insert dummy objects first and then map stringify over the result:

array = [
    {name: "abc", age: 22},
    {name: "xyz", age: 32},
    {name: "lmn", age: 23}]


result = array
    .flatMap(item => [{index: {}}, item])
    .map(x => JSON.stringify(x))
    .join('\n')

console.log(result)

// fs.writeFileSync('path/to/file', result)

answered Apr 21, 2021 at 11:36

georg

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Comments

T.J. Crowder · Accepted Answer · 2021-04-21 11:46:02Z

0

Note that the result isn't JSON (but it looks like valid JSON-Lines).

I wouldn't try to do string manipulation on the result of JSON.stringify. JSON is too complex for manipulation with basic regular expressions.

Instead, since you're outputting the contents of the array, handle each array entry separately:

const ws = fs.createWriteStream("data.json");
sourceData = data.map((key) => key['_source'])
for (const entry of sourceData) {
    const strData = JSON.stringify(entry);
    ws.write(`{"index":{}}\n${strData}\n`);
}
ws.end();
console.log("JSON data is saved.");

Live Example (obviously not writing to a file):

const sourceData = [
    {name:"abc", age:22},
    {name:"xyz", age:32},
    {name:"lmn", age:23}
];
for (const entry of sourceData) {
    const strData = JSON.stringify(entry);
    console.log(`{"index":{}}\n${strData}`); // Left off the trailing \n because console.log breaks up the lines
}
console.log("JSON data is saved.");

edited Apr 21, 2021 at 11:46

answered Apr 21, 2021 at 11:23

T.J. Crowder

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2 Comments

ahkam Over a year ago

the data.json file is empty. FYI i need the exact syntax, though it's not a perfect json file

T.J. Crowder Over a year ago

@MohamedAhkam - I should have been calling end() rather than destroy(). But if you want to build the entire string first and then write it, you can do it georg's way.

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