我该如何附加JavaScript？

Question

First off i'll state the obvious, i'm new to javascript,html, and web development tools.

var labels = {{ labels|tojson|safe }};

using console.log i was able to see the content of labels console.log(JSON.stringify(labels)); output:

[
    {"id":"1","image":"1-0.png","name":"","xMax":"4802","xMin":"4770","yMax":"156","yMin":"141"},
    {"id":"2","image":"1-0.png","name":"","xMax":"4895","xMin":"4810","yMax":"157","yMin":"141"},
    {"id":"3","image":"1-0.png","name":"","xMax":"4923","xMin":"4903","yMax":"156","yMin":"145"},
    {"id":"4","image":"1-0.png","name":"","xMax":"4956","xMin":"4931","yMax":"156","yMin":"145"}
]

It's clearly a list of dictionaries, so far so good, now there is new elements i want to append as it runs and WITHOUT REFRESHING THE PAGE Manually, it should auto update, so since i have some experience with python, i quickly thought about appending, something like that :

labels.append({"id":labels.length + 1, 
               "name":"",
               "xMin":xMin,
               "xMax":xMax,
               "yMin":yMin,
               "yMax":yMax
              })

but it isn't working, how can i append that line?

Answer 1

labels is a array type as it has

[{"id":"1","image":"1-0.png","name":"","xMax":"4802","xMin":"4770","yMax":"156","yMin":"141"},{"id":"2","image":"1-0.png","name":"","xMax":"4895","xMin":"4810","yMax":"157","yMin":"141"},{"id":"3","image":"1-0.png","name":"","xMax":"4923","xMin":"4903","yMax":"156","yMin":"145"},{"id":"4","image":"1-0.png","name":"","xMax":"4956","xMin":"4931","yMax":"156","yMin":"145"}]

So you need to use labels.push(obj) to add new object in the labels instead of append()

 var labels = [{"id":"1","image":"1-0.png","name":"","xMax":"4802","xMin":"4770","yMax":"156","yMin":"141"},{"id":"2","image":"1-0.png","name":"","xMax":"4895","xMin":"4810","yMax":"157","yMin":"141"},{"id":"3","image":"1-0.png","name":"","xMax":"4923","xMin":"4903","yMax":"156","yMin":"145"},{"id":"4","image":"1-0.png","name":"","xMax":"4956","xMin":"4931","yMax":"156","yMin":"145"}] var xMin = 1, xMax = 5, yMin = 3, yMax = 8; labels.push({"id":labels.length + 1, "name":"", "xMin": xMin, "xMax":xMax, "yMin":yMin, "yMax":yMax}); console.log(labels); 

Answer 2

Array.prototype.append() does not exist. You need to use Array.prototype.push() if you want to add to it:

Like this:

 var labels = [{"id":"1","image":"1-0.png","name":"","xMax":"4802","xMin":"4770","yMax":"156","yMin":"141"},{"id":"2","image":"1-0.png","name":"","xMax":"4895","xMin":"4810","yMax":"157","yMin":"141"},{"id":"3","image":"1-0.png","name":"","xMax":"4923","xMin":"4903","yMax":"156","yMin":"145"},{"id":"4","image":"1-0.png","name":"","xMax":"4956","xMin":"4931","yMax":"156","yMin":"145"}]; console.log(labels); labels.push({"id":labels.length + 1, "name":"name", "xMin":'xMin', "xMax":'xMax', "yMin":'yMin', "yMax":'yMax'}); console.log(labels);