JSON未捕获类型错误

Question

I am using the instagram API and if a caption doesnt exist or doesnt have text it doesnt include the node at all. So I included a check to see if caption exists which works, but if caption exists and the child node text does not, then I get the error: Uncaught TypeError: Cannot read property 'text' of null .

This is my code:

for (p in pictures) {
  if (pictures[p].hasOwnProperty('caption')) {
    if (pictures[p].caption.text != null) {
      captionString = pictures[p].caption.text;
    }
  }
}

Answer 1

Apparently, the caption property exists, but it seems to be null for some cases, and when you evaluate (null).text , you are getting the error detailed in your question.

Add pictures[p].caption && to evaluate for caption in your inner if .

This should work for you (note that I also merge your two if s and I did all evaluations in only one if ):

for(p in pictures) {
  if (pictures[p].hasOwnProperty('caption') && pictures[p].caption && pictures[p].caption.text != null) {
    captionString = pictures[p].caption.text;
  }
}

Answer 2

you could just try :

if(pictures[p].caption != null){
     captionString = pictures[p].caption.text;
}

instead of

if(pictures[p].hasOwnProperty('caption')){
     if(pictures[p].caption.text != null){
          captionString = pictures[p].caption.text;
     }
}

Because the caption property is always here, but may be null if not available