How do I check if a string/array/object exists in Javascript?
This question already has an answer here:
if(data != void(0) && data.unavailableItems != void(0)){
//exists
}
正如Norman在评论中指出的，你应该检查void 0意味着什么
A good tool to use for checking if an object contains a property is obj.hasOwnProperty(prop)
if(data.hasOwnProperty("unavailableItems")){
}
Also note, that a shim is available from John Resig for obj.hasOwnProperty
function hasOwnProperty(obj, prop) {
var proto = obj.__proto__ || obj.constructor.prototype;
return (prop in obj) &&
(!(prop in proto) || proto[prop] !== obj[prop]);
}
if ( Object.prototype.hasOwnProperty ) {
var hasOwnProperty = function(obj, prop) {
return obj.hasOwnProperty(prop);
}
}