Question 54106 in Javascript Question posted in
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Iterate object with custom index keys – Javascript

I have the following object, and I want to iterate and check the value of each object i.e. requestArr.st.value and if there is a value, then return the expr value.

var x = 12345
var y
const requestArr = {
  oj: {
    "value": x,
    "expr": "testX"
  },
  st: {
    "value": y,
    "expr": "testY"
  },
};

console.log(requestArr.oj.value)
console.log(requestArr.st.value)

for (const [index, key] of Object.keys(requestArr).entries()) {
 console.log(key)
}

Currently I can get the object index console.log(key) how do I navigate to test if there is a value and then return the expr?

update
I am still getting the expression for undefined value, I only want to return the expr for objects that contain a value in the value node.

for (const [index, key] of Object.keys(requestArr).entries()) {
  if (requestArr[key].value !== '' || requestArr[key].value !== undefined) {
    console.log(requestArr[key].value)
  }

}
Tags:

6

Answers


  1. 0

    You can iterate though object keys using for…in loop and inside loop check if requestArr[key].value exist then perform operation or store it in some array like this

    for(const key in requestArr){
    if(requestArr[key].value){
        console.log(requestArr[key].expr);
        // perform your stuff
    }
}

    Useinng Array.entries() method, you can use Array.forEach or Array.map as well,

    const displayValue = (key) => {
  if(requestArr[key].value){
        console.log(requestArr[key].expr);
        // perform your stuff and return value for Array.map and Array.filter
    }
}
// Array.entries
Object.keys(requestArr).entries(displayValue);
// Array.forEach 
Object.keys(requestArr).forEach(displayValue);
// Array.map 
Object.keys(requestArr).map(displayValue);
// Array.filter     
Object.keys(requestArr).filter(displayValue);
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  2. 0

    You can access the value of any key inside the Array by using the square brackets as such:

    requestArr[key]

    Using the key you have in the for loop you can test if the value is undefined by using:

    if(requestArr[key].value != undefined) {

    and then outputting the value if its not undefined as below:

    if(requestArr[key].value != undefined) {
  console.log(requestArr[key].value)
 }

    Below I have added this to your code:

    var x = 12345
var y
const requestArr = {
  oj: {
    "value": x,
    "expr": "testX"
  },
  st: {
    "value": y,
    "expr": "testY"
  },
};

for (const [index, key] of Object.keys(requestArr).entries()) {
 console.log("Key: " + key)
 if(requestArr[key].value != undefined) {
  console.log("Value not Undefined: " + requestArr[key].value)
 }
}
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  3. 0 
    var x = 12345
var y
const requestArr = {
  oj: {
    "value": x,
    "expr": "testX"
  },
  st: {
    "value": y,
    "expr": "testY"
  },
};


for (key in requestArr) {
  if (requestArr[key].value) {
    console.log(requestArr[key].expr)
  }
}
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  4. 0

    I’d go with Object.entries to access both key and value:

    var x = 12345;
var y;
const requestArr = {
  oj: {
    "value": x,
    "expr": "testX"
  },
  st: {
    "value": y,
    "expr": "testY"
  },
};

const validExpressions = Object.entries(requestArr)
  .map(([key, entry]) => !!entry.value && entry.expr)
  .filter((value) => !!value);

console.log(validExpressions);
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  5. 0

    You can filter the Object.values using Array.filter method:

    Object.values(requestArr).filter(entry => entry['value']);

    You can then add Array.forEach method anNd do whatever you want to do with the entry:

    Object.values(requestArr)
  .filter(entry => entry['value'])
  .forEach(entry => console.log(entry['expr']);

    ES5

    If you use ES5, as you updated your question, you need to loop over the object keys and map them to the object values like:

    Object.keys(requestArr)
  .map(function (key) {
    return requestArr[key];
  })
  .filter(function (entry) {
    return entry['value'];
  })
  .forEach(function (entry) {
    console.log(entry['expr']);
  })
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  6. 0

    Why do you have to invoke for .entries() ? you do not even use the index.

    This is much simpler and direct to the point in my opinion. And should solve your problem:

    Instead of

    for (const [index, key] of Object.keys(requestArr).entries())

    replace it with

    for (const key of Object.keys(requestArr))

    You are still getting the undefined value because you are using an || operator in your if statement. This should be using the &&,

    if (requestArr[key].value !== '' && requestArr[key].value !== undefined)

    You can further simplify this condition with
    if (requestArr[key].value)

    TLDR:

    Replace your for loop with this:

    for (const key of Object.keys(requestArr)) {
  if (requestArr[key].value) console.log(requestArr[key].value)
}
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