To push to an array with JavaScript, we use the push method.
For instance, we write
const json = [{ cool: "34.33" }, { alsocool: "45454" }];
json.push({ coolness: "34.33" });
to call json.push with an object to append it as the last item of the json array.
To reverse the order of an array using v-for and orderBy filter in Vue.js, we use the reverse method.
For instance, we write
<template>
<ul>
<li v-for="item in items.slice().reverse()">
//do something with item ...
</li>
</ul>
</template>
to make a copy of the items array with slice.
And we call reverse to return a reversed version of the copied array.
We then use v-for to render the items in the reversed array.
To create ul and fill it based on a passed array with JavaScript, we use the createElement and createTextNode methods.
For instance, we write
const options = ["Option 1", "Option 2"];
const makeUl = (array) => {
const list = document.createElement("ul");
for (const a of array) {
const item = document.createElement("li");
item.appendChild(document.createTextNode(a));
list.appendChild(item);
}
return list;
};
document.getElementById("foo").appendChild(makeUl(options));
to define the makeUl function.
In it, we create the ul element with createElement.
Then we loop through the array with a for-of loop.
In the loop, we create a li element with createElement.
Then we create a text node with the a content as the text with createTextNode.
Then we call item.appendChild to append the text node to the li as its last child.
And we call list.appendChild to append the li to the ul as its last child.
We then return the list.
Finally, we call makeUl with options and call appendChild to append that as the last child of the element with ID foo.
To convert Map to JSON object in JavaScript, we use the Object.fromEntries method.
For instance, we write
const map1 = new Map([
["foo", "bar"],
["baz", 42],
]);
const obj = Object.fromEntries(map1);
to create a map with the Map constructor.
Then we call Object.fromEntries with map1 to convert it to an array of key-value pair arrays.
To check whether multiple values exist within a JavaScript array, we use the every and includes methods.
For instance, we write
const success = arrayA.every((val) => arrayB.includes(val));
to call arrayA.every with a callback that checks if every val in arrayA is in “arrayBwithincludes`.
If the condition is met for all elements in arrayA, then true is return.