JSFiddle - React, Tailwind, and code Playground

HTML

<div id="result"></div>

JavaScript

var testArray=[];

testArray.push({"key1":"value1","key2":"value2"});
testArray.push({"key1":"value11","key2":"value22"});

var filtered = testArray.filter(function(item) {
    if (item.key1 == 'value11') {
    	item.key3 = 'valuue33';
    	return true
    }
    return false;
});

$('#result').html(JSON.stringify(filtered));