How to delete a javascript object item by value?

Have you tried something like this?

function deleteByValue(val) {
    for(var f in fruits) {
        if(fruits[f] == val) {
            delete fruits[f];
        }
    }
}

And as per Rocket's comment, you might want to check hasOwnProperty to make sure you aren't deleting members of the object's prototype:

function deleteByValue(val) {
    for(var f in fruits) {
        if(fruits.hasOwnProperty(f) && fruits[f] == val) {
            delete fruits[f];
        }
    }
}

var key = null;
for (var k in fruits){
  if (fruits[k] === 'apple'){
    key = k;
    break;
  }
}
if (key != null)
  delete fruits[key];

Iterate over the object finding the corresponding key, then remove it (if found).

Don't know if this is efficient in terms of processing but using filter you can get this done in three lines:

var fruits = {
    "red" : "apple",
    "blue" : "blueberry",
    "yellow" : "banana"
}

var appleless_keys = Object.keys(fruits).filter(this_fruit => fruits[this_fruit] !== "apple");
appleless_obj = {};
appleless_keys.forEach(key => appleless_obj[key] = fruits[key]);
console.dir(appleless_obj);

Or as a function:

var fruits = {
    "red" : "apple",
    "blue" : "blueberry",
    "yellow" : "banana"
}

function remove_fruit(fruit_to_remove,fruits){
  var new_keys = Object.keys(fruits).filter(this_fruit => fruits[this_fruit] !== fruit_to_remove);
  new_obj = {};
  new_keys.forEach(key => new_obj[key] = fruits[key]);  
  return new_obj;
}

console.dir(remove_fruit("apple",fruits));

Simplified using key deletion,

function stripProperty(o, v) {
    return  (delete o[Object.keys(o).splice(Object.values(o).indexOf(v), 1)])?o:0;
}   

    var fruits = {
        "red" : "apple",
        "blue" : "blueberry",
        "yellow" : "banana"
    }

    function stripProperty(o, v) {
        return  (delete o[Object.keys(o).splice(Object.values(o).indexOf(v), 1)])?o:0;
    }   


    console.log(stripProperty(fruits, 'banana'));

Usage,

var fruits = {
    "red" : "apple",
    "blue" : "blueberry",
    "yellow" : "banana"
}

console.log(stripProperty(fruits, 'apple'))

what about this one?

function delteByValue(a){
  fruits.foreach( function( k, v ) {
    if (fruits[v] == a){
      delete fruits[k];
    }
  });
}

I think its a good idea to create a function and override the Object.prototype:

/**
 *  @autor Javier Cobos
 *  @param value The value to look for
 *  @return true if founded deleted, false if not
 */        
Object.prototype.removeByValue = function(value){
         var i;
         for(i in this){
            if(this.hasOwnProperty(i))
                if(value === this[i]){
                   delete(this[i]);
                   return true;
                }
         }   
         return false;
        }

// Example
     var fruits = {
        "red" : "apple",
        "blue" : "blueberry",
        "yellow" : "banana"
    }

        fruits .removeByValue("apple");

This way we have a new method for every single Object in our script :)

I know you have several acceptable answers at this point... I'm going to include a generic function for this...

// NOTE, replace "Object.removePropertyByValue" 
// with say "jQuery.removePropertyByValue" or "_.removePropertyByValue"
// to create a jQuery or Underscore extension.
Object.removePropertyByValue = function(obj, val) {
  //store list of properties to remove
  var propsToRemove = [];

  for (var prop in obj) {
    if (obj.hasOwnProperty(prop) && obj[prop] === val) {
      //save the property name here, deleting while enumerating is a bad idea.
      propsToRemove.push(prop);
    }
  }

  //remove all the items stored.
  while (propsToRemove.length) delete obj[propsToRemove.pop()];
}

From here you should be able to call: Object.removePropertyByValue(fruits, "red");

use this function

function delobj(obj,val){
    for (x in obj) {
        if(obj[x] == val)
        delete obj[x]
    }
    return obj;
}

use like this

delobj(object "object name",string "value of element")

You can use the splice method

fruits.splice($.inArray("red", fruits), 1);

But this uses jQuery of course.

You can also use this extension:

Array.prototype.remove = function () {
    var what, a = arguments, L = a.length, ax;
    while (L && this.length) {
        what = a[--L];
        while ((ax = this.indexOf(what)) != -1) {
            this.splice(ax, 1);
        }
    }
    return this;
}