Logic

• Loop through keys each item in items array.
• Check if the key name is not props.
• Add the key value combination to an object except for key props
• Loop through the props node in each object.
• Add each prop to props key and push it to final array
• You should perform a deep copy logic here, sice you are keep on updating the pushong object

var items = [{
  id: 1,
  name: "item name",
  props: [
    { propId: 1, propName: "name one" }, 
    { propId: 2, propName: "name two" },
    { propId: 3, propName: "name three" }
  ]
}];
var desiredOutput = [];
for (var index = 0; index < items.length; index++) {
  var outputNode = {};
  var entries = Object.entries(items[index]);
  for(var innerIndex = 0; innerIndex < entries.length; innerIndex++) {
    if(entries[innerIndex][0] !== 'props') {
      outputNode[entries[innerIndex][0]] = entries[innerIndex][1];
    }
  }
  for(var innerIndex = 0; innerIndex < items[index].props.length; innerIndex++) {
    outputNode.props = [items[index].props[innerIndex]];
    // This is mandatory to perform deep copy
    desiredOutput.push(JSON.parse(JSON.stringify(outputNode)));
  }
}
console.log(desiredOutput);

You can use something like this:

function copyProps(itemsArr) {
  var copy = []; var i = 0;
  
  itemsArr.forEach(function(item) {
    item.props.forEach(function(prop) {
      copy[i] = Object.assign({}, item);
      copy[i].props = [Object.assign({}, prop)];
      i++;
    });
  }); 
  
  return copy;
}

just another way of getting the desired output with deep copy.

var items = [{
  id: 1,
  name: "item name",
  props: [{
    propId: 1,
    propName: "name one"
  }, {
    propId: 2,
    propName: "name two"
  }, {
    propId: 3,
    propName: "name three"
  }]
}];

var desiredOutput = [];

function ExtractDataFromProp(jsObject, jsObjectPropKey) {
    if (Object.hasOwnProperty.call(jsObject, jsObjectPropKey)) {
        const propElementValue = jsObject[jsObjectPropKey];
        if (typeof propElementValue != "object") {
            const propString = `"${jsObjectPropKey}" : ${isNaN(propElementValue) ? ("\"" + propElementValue + "\"") : propElementValue}`;
            return propString;
        }
        return null;
    }
}

items.forEach((item) => {
    var itemObjArray = [];
    var itemProps = [];

    for (const itemKey in item)
        itemObjArray.push(ExtractDataFromProp(item, itemKey));

    item.props.forEach((prop) => {
        for (const propKey in prop)
            itemProps.push(ExtractDataFromProp(prop, propKey));

        var finalObject = `{ ${itemObjArray.join(',').replace(/,\s*$/, "")}, "props": { ${itemProps.join(',').replace(/,\s*$/, "")} } }` //

        desiredOutput.push(JSON.parse(finalObject))

    });
});

console.dir(desiredOutput);