Modifying an array is just like modifying an object when that array is inside the object. The normal general principles will apply here.
Example
In the following example, Initially in the 'companies' array, the first element is 'Tesla'. But after modifying the first element is changed to 'SolarCity' and the result is displayed in the output.
<html>
<body>
<script>
var res1 = "";
var res2 = "";
var obj = {
"name":"Elon musk",
"age":48,
"companies": [
"Tesla", "Spacex", "Neuralink"
]
}
for (var i in obj.companies) {
res1 += obj.companies[i] + "</br>"
}
document.write("Before change: " +" "+res1);
obj.companies[0] = "SolarCity";
for (var i in obj.companies) {
res2 += obj.companies[i] + "</br>"
}
document.write("After change:" +" "+res2);
</script>
</body>
</html>Output
Before change: Tesla Spacex Neuralink After change: SolarCity Spacex Neuralink