I want to convert a math operation in Javascript. For example given a "-", it should get converted to a "+", "*" - "/" and so on.
My current code is a switch case, which is really slow to perform:
if (contents.className == "buttonfunction") {
if (invert == true) {
switch (contents.innerHTML) {
case "+":
contents.innerHTML = "-";
break;
case "-":
contents.innerHTML = "+";
break;
case "*":
contents.innerHTML = "/";
break;
case "/":
contents.innerHTML = "*";
break;
}
}
document.body.appendChild(contents);
}
Is there a better/faster solution to this problem?
Performance will be negligible but for operations that map a thing to another thing, a table-driven approach is often more maintainable in the long run:
const inverseOperations = {
'+': '-',
'-': '+',
'/': '*',
'*': '/',
};
if (contents.className == "buttonfunction") {
const operation = contents.innerHTML
if (invert == true && inverseOperations[operation]) {
contents.innerHTML = inverseOperations[operation];
}
document.body.appendChild(contents);
}
I added some context to make a running example.
By the way the approach used here is a map of rules for inversion, replacing the logic you were using in your switch statement:
let invert = true;
//granular map of pairs declaring the inverse of each operator
//it could be declared inline here but it could be also fed with the addInversionInMap
let inverted = {}; //{ '+' : '-', '-' : '+', '*' : '/', '/' : '*'}
addInversionInMap('+','-');
addInversionInMap('*','/');
//feeds the inverted map without repeating the both the sides in declaration
function addInversionInMap(op, opInverted){
inverted[op] = opInverted;
inverted[opInverted] = op;
}
//on document ready adds the click handler to every .buttonfunction elements
document.addEventListener("DOMContentLoaded", function() {
addClickHandlerToButtonsFunction();
});
//adds the handler for click event on .buttonfunction
function addClickHandlerToButtonsFunction(){
let btns = Object.values(document.getElementsByClassName('buttonfunction'));
for(let btn of btns){
btn.addEventListener('click', invertValue);
}
}
//return the inverted operator based on the inverted map
//(or return the operator as is if there's no way to invert)
function getInvert(operator){
if(inverted.hasOwnProperty(operator))
return inverted[operator];
else
return operator;
}
//inverts the value of the element whose id is declared in the data-target attribvute
//of the button that triggered the click event (such element should be input type text)
function invertValue(){
let contents = window.event.target;
if (contents.className == "buttonfunction") {
if (invert == true) {
let targetId = contents.getAttribute('data-target');
let target = document.getElementById(targetId);
//I'm using value so I expect the element to be input type text
target.value = getInvert(target.value);
}
}
}button.buttonfunction{
cursor: pointer;
}<input id="input" type="text"></input>
<button type="button" class="buttonfunction" data-target="input">Invert</button>