javascript - この配列の倍数を置き換える方法は?

Question

array = ['blue', 'red', 'green', 'green', 'red', 'blue', 'black', 'blue']

...私が達成しようとしている出力は、

output = ['blue x3', 'red x2', 'green x2', 'black']

これを行うための最も効果的な方法を見つけるのに苦労しています。

ありがとう！

Answer 1

 var array = ['blue', 'red', 'green', 'green', 'red', 'blue', 'black', 'blue'] 

 var hash = {};
 for( var i = 0; i < array.length; ++i){
     hash[array[i]] = (!hash.hasOwnProperty(array[i]) ? 1 : hash[array[i]]+1);
 }

 var output = [];
 for(var key in hash){
     output.push( key + (hash[key]>1 ? (" x"+hash[key]):"") );
 }
 console.log( output ); //["blue x3", "red x2", "green x2", "black"]

デモ

Answer 2

// You can use an object to group strings
var colourGroups = {};
var array = ['blue', 'red', 'green', 'green', 'red', 'blue', 'black', 'blue'];

// loop and group each colour. 
array.forEach(function(colourName) {

    if (colourGroups[colourName] )
        // increment the count
        colourGroups[colourName]++;
    else
        //initialize the property with 1
        colourGroups[colourName] = 1;

});    


// display results
var results = [];

for(var prop in colourGroups) {
    var colourCountStats = prop + " x " + colourGroups[prop];
    results.push(colourCountStats );
}

console.log(results);
document.write(results);​

JSフィドルの例：http：//jsfiddle.net/peterf/J7EUc/

Answer 3

var arr =  ['blue', 'red', 'green', 'green', 'red', 'blue', 'black', 'blue'];

var group = {};
for (var i = arr.length; --i >= 0;) {
  var value = arr[i];
  group[value] = 1 - -(group[value] | 0);
}
var result = [];
for (e in group) { 
  result.push(e + ' x' + group[e]);
}

Answer 4

これが私がすぐに思いついた安っぽい解決策です。

var array = ['blue', 'red', 'green', 'green', 'red', 'blue', 'black', 'blue'],
    output = [], temp = {}, i;

// loop through array and count the values
array.forEach(function(a){
    temp[a] = temp[a] ? temp[a]+1 : 1;
});

// loop though temp and add "xN" to the values
for(i in temp){
    output.push(i + (temp[i] > 1 ? ' x'+temp[i] : ''));
}

console.log(output);

注：.forEachIE 8（またはそれ以前）では機能しません。