57 lines
1.6 KiB
JavaScript
57 lines
1.6 KiB
JavaScript
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"use strict";
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const $ = selector => document.querySelector(selector);
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const isInvalidValue = val => {
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if (isNaN(val)) {
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console.error("Value is not a number");
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} else if (val <= 0) {
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console.error(`Value ${val} is not greater than zero.`);
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}
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return isNaN(val) || val <= 0
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};
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const focusAndSelect = selector => {
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const elem = $(selector);
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elem.focus();
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elem.select();
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};
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const processEntries = () => {
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console.log("processEntries function has started");
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// clear previous calculation
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$("#mpg").value = "";
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const miles = parseFloat($("#miles").value);
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const gallons = parseFloat($("#gallons").value);
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console.log("miles = " + miles);
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console.log("gallons = " + gallons);
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let errorMessage = "";
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if (isInvalidValue(miles)) {
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errorMessage += "Miles driven must be a valid number greater than zero.\n";
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focusAndSelect("#miles");
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}
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if (isInvalidValue(gallons)) {
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errorMessage += "Gallons of gas used must be a valid number greater than zero.";
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focusAndSelect("#gallons");
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}
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if (errorMessage == "") {
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console.log("The data is valid and the calculation is next");
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const mpg = miles / gallons;
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console.log("mpg = " + mpg);
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$("#mpg").value = mpg.toFixed(2);
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} else {
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alert(errorMessage);
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}
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};
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document.addEventListener("DOMContentLoaded", () => {
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$("#calculate").addEventListener("click", processEntries);
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$("#miles").focus();
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});
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