这种表达式是啥意思
var gDLVersions = {
"fx": {
"1.0.6": "firefox-1.0.6",
"1.0.5": "firefox-1.0.5",
"1.0.4": "firefox-1.0.4",
"1.0.3": "firefox-1.0.3",
"1.0.2": "firefox-1.0.2",
"1.0.1": "firefox-1.0.1",
"1.0": "firefox"
},
"tb": {
"1.0.6": "thunderbird-1.0.6",
"1.0.5": "thunderbird-1.0.5",
"1.0.2": "thunderbird-1.0.2",
"1.0": "thunderbird"
}
};