What is the best way to add content in JavaScript?

Just diving into the world of JavaScript, HTML, and web development tools here. 

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

After using console.log to check the content of labels with 

console.log(JSON.stringify(labels));
, I got this 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 seems like a list of dictionaries. Now my goal is to auto-update new elements without having to refresh the page manually. With some background in Python, I attempted to append by writing this line of code: 

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

However, I'm encountering issues making it work. Any tips on how to successfully append that line?

javascriptajax

Answer №1

labels is considered an array type due to the presence of:

[{"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"}]

To add a new object to the labels, you should use labels.push(obj) 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() is not a valid method. To add elements to an array, you should use Array.prototype.push():

For example:

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":"","xMa...

console.log(labels);


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

console.log(labels);

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