number-i18n.js

var number = 10000.20;
console.log('default (' + window.navigator.language + '): ' + number.toLocaleString());
console.log('fr-FR: ' + number.toLocaleString('fr-FR'));
console.log('fr: ' + number.toLocaleString('fr'));
console.log('en-US: ' + number.toLocaleString('en-US'));
console.log('en: ' + number.toLocaleString('en'));
console.log('ja: ' + number.toLocaleString('ja'));
console.log('zh: ' + number.toLocaleString('zh'));

Gecko Firefox/39.0

Accept-Language: en,fr;q=0.7,en-US;q=0.3
default (en): 10 000,2
fr-FR: 10 000,2
fr:    10 000,2
en-US: 10,000.2
en:    10,000.2
ja:    10,000.2
zh:    10,000.2

Blink OPR/29.0.1795.30

Accept-Language: fr-FR,fr;q=0.8,en-US;q=0.6,en;q=0.4
default (fr): 10 000,2
fr-FR: 10 000,2
fr:    10 000,2
en-US: 10,000.2
en:    10,000.2
ja:    10,000.2
zh:    10,000.2

Webkit Safari/600.4.10

Accept-Language: fr-fr
default (fr-fr): 10000.2
fr-FR: 10000.2
fr:    10000.2
en-US: 10000.2
en:    10000.2
ja:    10000.2
zh:    10000.2

Trident Internet Explorer 11 or Spartan Edge

Accept-Language: 
default (en-US): 10,000.2
fr-FR: 10 000,2
fr:    10 000,2
en-US: 10,000.2
en:    10,000.2
ja:    10,000.2
zh:    10,000.2