如何遍历数组字典（不知道键名）

Question

I have a an object that looks similar to this:

[
    {"key1": ["2019-04-12-14:54:29.190", "19", "0", "4325", "1"]},
    {"key2": ["2019-04-12-14:54:29.191", "20", "0", "2212", "1"]},
    {"key3": ["2019-04-12-14:54:29.192", "22", "0", "4376", "0"]}
]

However I do NOT know the names of the keys (ie key1, key2 and key3 names are not known to me).

This post is almost exactly what I want, except that method requires you to know the names of the keys.

I need to be able to iterate over the key name and it's value array.

I've tried this:

for (var i in zk) {
    for (var j in zk[i]) {
        console.log(j)
    }
}

But that only prints the key names. How can I iterate through the list as well? In most langues iterating over j seems the logical choice but not in this case. Any ideas? Thank you.

Answer 1

Let's continue from the code sample you have provided.

1) Getting the keys of each element

for (let i in zk) {
  for (let j in zk[i]) {
    console.log(j)
  }
}

2) Getting the list within each element

for (let i in zk) {
  for (let j in zk[i]) {
    console.log(zk[i][j])
  }
}

3) Iterating through each list within each element

for (let i in zk) {
  for (let j in zk[i]) {
    for (let k = 0; k < zk[i][j].length; k++) {
      console.log(zk[i][j][k])
    }
  }
}

Alternatively, you can use Object.values , which returns the values of each key-value pair. You can consider using Array.map() too.

for (let i in zk) {
  Object.values(zk[i]).map(list => {
    list.map(element => {
      console.log(element);
    });
  });
}

Answer 2

You could take a differetn approach for iterating the given arrays and objects, with

• Array#forEach for iterating an array,

• Object.entries for getting an array of arrays with keys and values and a

• destructuring assignment for an array of key/value pairs.

 var data = [{ key1: ["2019-04-12-14:54:29.190", "19", "0", "4325", "1"] }, { key2: ["2019-04-12-14:54:29.191", "20", "0", "2212", "1"] }, { key3: ["2019-04-12-14:54:29.192", "22", "0", "4376", "0"] }]; data.forEach((object, outerIndex) => Object.entries(object).forEach(([key, array]) => array.forEach((value, innerIndex) => console.log(outerIndex, key, innerIndex, value) ) ) ); 

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Answer 3

You missed the object of which value has to be printed

for (var i in zk) {
    for (var j in zk[i]) {
        console.log(zk[i][j])
    }
}

Answer 4

The issue is that you're missing one level of your loop. You have to loop over the outer array, then loop over the keys in each object, then if that key's value is an array loop over that array.

If for example you want to log all the values then you can use Object.prototype.keys() it returns an array of the keys in an object so you can try something like this:

 const arr = [ {"key1": ["2019-04-12-14:54:29.190", "19", "0", "4325", "1"]}, {"key2": ["2019-04-12-14:54:29.191", "20", "0", "2212", "1"]}, {"key3": ["2019-04-12-14:54:29.192", "22", "0", "4376", "0"]} ]; arr.forEach(x => { Object.keys(x).forEach(k => { if (Array.isArray(x[k])) { x[k].forEach(v => { console.log(v); }); } else { console.log(x[k]); } }); }); 

Answer 5

Object.entries would be helpful if you are trying to iterate over and output each object key and each of the values in the corresponding array. There are more compact ways to do this, but the nested loops should clearly illustrate what is happening.

 const arr = [ {"key1": ["2019-04-12-14:54:29.190", "19", "0", "4325", "1"]}, {"key2": ["2019-04-12-14:54:29.191", "20", "0", "2212", "1"]}, {"key3": ["2019-04-12-14:54:29.192", "22", "0", "4376", "0"]} ]; for (let obj of arr) { for (let [key, values] of Object.entries(obj)) { console.log(`KEY: ${key}`); console.log('VALUES: '); for (let value of values) { console.log(value); } } } // Example output from first object... // KEY: key1 // VALUES: // 2019-04-12-14:54:29.190 // 19 // 0 // 4325 // 1 

Answer 6

In js you always get the keys so what you do is:

for (var i in zk) {
    for (var j in zk[i]) { // j wil ben key1, key2 ect
        console.log(zk[i][j]); // arrays  ["2019-04-12-14:54:29.190", "19", "0", "4325", "1"] over where you can itterate
        for (var k in zk[i][j]) {
            console.log(zk[i][j][k]); // "2019-04-12-14:54:29.190" ect
        }
    }
}

Answer 7

Use Object.values :

 const arr = [ {"key1": ["2019-04-12-14:54:29.190", "19", "0", "4325", "1"]}, {"key2": ["2019-04-12-14:54:29.191", "20", "0", "2212", "1"]}, {"key3": ["2019-04-12-14:54:29.192", "22", "0", "4376", "0"]} ]; arr.forEach(obj => console.log(Object.values(obj))); 

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