Javascript: how to dynamically create nested objects using object names given by an array

Put in a function, short and fast.

var createNestedObject = function( base, names ) {
    for( var i = 0; i < names.length; i++ ) {
        base = base[ names[i] ] = base[ names[i] ] || {};
    }
};

// Usage:
createNestedObject( window, ["shapes", "triangle", "points"] );
// Now window.shapes.triangle.points is an empty object, ready to be used.

Skips already existing parts of the hierarchy. Useful if you are not sure whether the hierarchy was already created.

Or:

A fancier version where you can directly assign the value to the last object in the hierarchy, and you can chain function calls because it returns the last object.

// Function: createNestedObject( base, names[, value] )
//   base: the object on which to create the hierarchy
//   names: an array of strings contaning the names of the objects
//   value (optional): if given, will be the last object in the hierarchy
// Returns: the last object in the hierarchy
var createNestedObject = function( base, names, value ) {
    // If a value is given, remove the last name and keep it for later:
    var lastName = arguments.length === 3 ? names.pop() : false;

    // Walk the hierarchy, creating new objects where needed.
    // If the lastName was removed, then the last object is not set yet:
    for( var i = 0; i < names.length; i++ ) {
        base = base[ names[i] ] = base[ names[i] ] || {};
    }

    // If a value was given, set it to the last name:
    if( lastName ) base = base[ lastName ] = value;

    // Return the last object in the hierarchy:
    return base;
};

// Usages:

createNestedObject( window, ["shapes", "circle"] );
// Now window.shapes.circle is an empty object, ready to be used.

createNestedObject( window, ["shapes", "rectangle", "width"], 300 );
// Now we have: window.shapes.rectangle.width === 300

createNestedObject( window, "shapes.rectangle.height".split('.'), 400 );
// Now we have: window.shapes.rectangle.height === 400

Note: if you need values different than standard objects (ie. not {}) in your hierarchy, see also TimDog's answer.

Edit: uses regular loops instead of for...in loops. It's safer in cases where a library modifies the Array prototype.

Here is a simple tweak to jlgrall's answer that allows setting distinct values on each element in the nested hierarchy:

var createNestedObject = function( base, names, values ) {
    for( var i in names ) base = base[ names[i] ] = base[ names[i] ] || (values[i] || {});
};

Hope it helps.

try using recursive function:

function createSetting(setting, value, index) {
  if (typeof index !== 'number') {
    index = 0;
  }

  if (index+1 == setting.length ) {
    settings[setting[index]] = value;
  }
  else {
    settings[setting[index]] = {};
    createSetting(setting, value, ++index);
  }
}

I think, this is shorter:

Settings = {};
newSettingName = "Modules_Floorplan_Image_Src";
newSettingValue = "JWPlayer";
newSettingNameArray = newSettingName.split("_");

a = Settings;
for (var i = 0 in newSettingNameArray) {
    var x = newSettingNameArray[i];
    a[x] = i == newSettingNameArray.length-1 ? newSettingValue : {};
    a = a[x];
}