undefined

问题 I have a scenario where I'm passing data from a reducer into my react state. data: { "id": 1, "title": "Test", "content": { "body": "sdfsdf" "image": "http://example.com" } } Using componentWillRecieveProps, this works perfectly for retrieving the title. componentWillReceiveProps(nextProps) { this.setState({ title: nextProps.blog.title, }) } However, I'm having difficulty retrieving the nested fields. When I do this: componentWillReceiveProps(nextProps) { console.log("new title is", nextProps

问题 This question already has answers here : JavaScript check if variable exists (is defined/initialized) (24 answers) Closed 3 years ago . I am trying to test to see whether a Javascript variable is undefined. You will see that I am not expecting the value of predQuery[preId] to be 'undefined' if I don't first get an alert saying "its unbelievable". But I often do, so I am guessing that my statement predQuery[preId]=='undefined') is not matching the undefined elements properly. if((predQuery

问题 This question already has answers here : JavaScript check if variable exists (is defined/initialized) (24 answers) Closed 3 years ago . I am trying to test to see whether a Javascript variable is undefined. You will see that I am not expecting the value of predQuery[preId] to be 'undefined' if I don't first get an alert saying "its unbelievable". But I often do, so I am guessing that my statement predQuery[preId]=='undefined') is not matching the undefined elements properly. if((predQuery

问题 I've looked a fair bit, so pardon me if this has already been answered. I'm also curious as to what the actual term is called; Is it "Ambiguous" for the type of arguments I am handling? Anyways, the problem is that I want to be able to call a function like this: prompt(_.define(variable, "DEFAULT VALUE")); Basically, so that variables can have default values. However, every time I try to do this, I get this error: Timestamp: 6/11/2012 1:27:38 PM Error: ReferenceError: thisvarisnotset is not

问题 I have a simple php structures. class Ingredient and class Ingredients, i have this code: class Ingredient { public function objectIsValid() { return $validate[0]; } } class Ingredients { public $ingObject; function __construct(){ $ingObject = new Ingredient(); } public function validateData() { if($this->ingObject->objectIsValid() /*** THE ERROR ***/) { echo "OK";} else { echo "NOT";} } } $Ingridients = new Ingredients(); $Ingridients->validateData(); I just can't understand why do i get the

问题 I was wondering if anyone could explain me why this function return undefined instead of founded object var people = [ {name: 'John'}, {name: 'Dean'}, {name: 'Jim'} ]; function test(name) { people.forEach(function(person){ if (person.name === 'John') { return person; } }); } var john = test('John'); console.log(john); // returning 'undefined' 回答1: Returning into forEach loop won't work, you are on the forEach callback function, not on the test() function. So instead you need to return the

问题 I was working off of the answer in this question: Python Interactive Shell Type Application My code looks like this def main(): while True: s = input('> ') if s == 'hello': print('hi') if s == 'exit': break if __name__ == "__main__": main() If I run it, and type hello, I get File "<string>", line 1, in <module> NameError: name 'hello' is not defined How should I be listening for text, and calling different functions based on the result? 回答1: You're running it under Python 2.x, where input()

问题 I was working off of the answer in this question: Python Interactive Shell Type Application My code looks like this def main(): while True: s = input('> ') if s == 'hello': print('hi') if s == 'exit': break if __name__ == "__main__": main() If I run it, and type hello, I get File "<string>", line 1, in <module> NameError: name 'hello' is not defined How should I be listening for text, and calling different functions based on the result? 回答1: You're running it under Python 2.x, where input()

问题 On this page, it shows some example code, containing the following line: var Subject = ( function( window, undefined ) { What is the undefined as a function parameter? 回答1: This is used to prevent from overriding the value of undefined in non-strict mode. In non-strict mode, the value of undefined can be override by assigning other value to it. undefined = true; // Or any other value So, using the value of undefined will not work as expected. In strict-mode, undefined is read-only and

问题 I have downloaded the iProcessing framework (lets you build native javascript apps for iPhone) and when I try to compile, I get: Undefined symbols for architecture i386: "_ADBannerContentSizeIdentifier320x50", referenced from: -[TiUIiOSAdViewProxy SIZE_320x50] in TiUIiOSAdViewProxy.o "_ADBannerContentSizeIdentifier480x32", referenced from: -[TiUIiOSAdViewProxy SIZE_480x32] in TiUIiOSAdViewProxy.o "_OBJC_CLASS_$_ADBannerView", referenced from: objc-class-ref in TiUIiOSAdView.o ld: symbol(s)