49 lines
1.4 KiB
JavaScript
49 lines
1.4 KiB
JavaScript
"use strict";
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const $ = selector => document.querySelector(selector);
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const getNumericErrorMsg = lbl => `${lbl} must be a valid number.`;
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const getRangeErrorMsg = lbl => `${lbl} must be greater than zero.`;
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const focusAndSelect = selector => {
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const elem = $(selector);
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elem.focus();
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elem.select();
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};
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const processEntries = () => {
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const miles = parseFloat($("#miles").value);
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const gallons = parseFloat($("#gallons").value);
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if (isNaN(miles)) {
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alert(getNumericErrorMsg("Miles driven"));
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focusAndSelect("#miles");
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} else if (miles <= 0) {
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alert(getRangeErrorMsg("Miles driven"));
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focusAndSelect("#miles");
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}
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else if (isNaN(gallons)) {
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alert(getNumericErrorMsg("Gallons of gas used"));
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focusAndSelect("#gallons");
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} else if (gallons <= 0) {
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alert(getRangeErrorMsg("Gallons of gas used"));
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focusAndSelect("#gallons");
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}
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else {
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$("#mpg").value = (miles / gallons).toFixed(2);
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}
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};
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const clearEntries = () => {
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$("#miles").value = "";
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$("#gallons").value = "";
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$("#mpg").value = "";
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$("#miles").focus();
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}
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document.addEventListener("DOMContentLoaded", () => {
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$("#calculate").addEventListener("click", processEntries);
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$("#clear").addEventListener("click", clearEntries);
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$("#miles").addEventListener("dblclick", clearEntries);
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$("#miles").focus();
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}); |