Programming Tutorials

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Verifying user input in JavaScript

By: Dave Reed in Javascript Tutorials on 2011年01月28日 [フレーム]

This javascript library contains functions for verifying the contents of a text box. For each function the name of a text box is passed as input, along with any restrictions on the contents. If the contents of the box are not legal, a warning is displayed.

function verifyNum(textBox)
 // Assumes: textBox is a text box in the page
 // Results: warns if box contents is not a number
 {
 var boxValue;
 boxValue = parseFloat(textBox.value);
 if ( isNaN(boxValue) ) {
 alert("You must enter a number value!");
 }
 }
 function verifyNumInRange(textBox, low, high)
 // Assumes: textBox is a text box in the page, low <= high // Results: warns if box contents is not a number in range low..high { var boxValue; boxValue = parseFloat(textBox.value); if ( isNaN(boxValue) || (boxValue < low) || (boxValue> high)) {
 alert("You must enter a number value in the range [" +
 low + ".." + high + "]");
 }
 }
 function verifyInt(textBox)
 // Assumes: textBox is a text box in the page
 // Results: warns if box contents is not an integer
 {
 var boxValue;
 boxValue = parseFloat(textBox.value);
 if ( isNaN(boxValue) || (boxValue % 1 != 0) ) {
 alert("You must enter an integer value!");
 }
 }
 function verifyIntInRange(textBox, low, high)
 // Assumes: textBox is a text box in the page, low <= high // Results: warns if box contents is not an integer in range low..high { var boxValue; boxValue = parseFloat(textBox.value); if ( isNaN(boxValue) || (boxValue % 1 != 0) || (boxValue < low) || (boxValue> high)) {
 alert("You must enter an integer value in the range [" +
 low + ".." + high + "]");
 }
 }
 function verifyOneOf(textBox, options)
 // Assumes: textBox is a text box in the page, options is a list
 // Results: warns if box contents is not one of the options
 {
 for (i = 0; i < options.length; i++) { if (textBox.value == options[i]) { return; } } alert("You must enter one of the following: " + options); }

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