如果颜色值无效-JavaScript-前端问题

If color value is not valid - JavaScript(如果颜色值无效-JavaScript)

本文介绍了如果颜色值无效-JavaScript的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

我的JavaScript代码有问题如果您输入了错误的代码(颜色值)，则它一定是黑色的。但当我输入类似"blabla"的内容时，我会输入最后一个作为示例：我写红色，然后它将是一个红色的圆圈，但在那之后，当我写blabla时，它也将是红色的，我只是希望当我写错颜色的单词时，它将是黑色的我想我必须写一个RGB代码，这样函数才能检查我写的是对还是错

function getPos(canvas, event){

    var a = new Number();
    var b = new Number();
    var canvas= document.getElementById("can1");

    if (event.a != undefined && event.b != undefined)
    {
      a = event.a;
      b = event.b;
    }
    else
    {
      a = event.clientX + document.body.scrollLeft +
          document.documentElement.scrollLeft;
      b = event.clientY + document.body.scrollTop +
          document.documentElement.scrollTop;
    }
    a -= canvas.offsetLeft;
    b -= canvas.offsetTop;




    var ctx = canvas.getContext("2d");
    var color1 = document.getElementById('color');
    var size = document.getElementById('size');
    ctx.beginPath();

    if ( size.value > 0)
        {
        ctx.arc(a,b,size.value, 275*(Math.PI/180), 635*(Math.PI/180), false);
        }
    else
        {
        ctx.arc(a,b,15, 275*(Math.PI/180), 635*(Math.PI/180), false);
        } 




    if (color1.value.length < 0)
        {   
        ctx.fillStyle = "#000000";

        }

    else if (color1.value.length == 0) 
        {
        ctx.fillStyle = '#000000';
        }

    else
        {
        ctx.fillStyle = color1.value; 
        }



        ctx.fill();
        ctx.stroke();
        ctx.closePath();
        window.localStorage['IMG'] = canvas.toDataURL();
}

我想问题在这里：

if (color1.value.length < 0)
        {   
        ctx.fillStyle = "#000000";

        }

    else if (color1.value.length == 0) 
        {
        ctx.fillStyle = '#000000';
        }

    else
        {
        ctx.fillStyle = color1.value; 
        }

推荐答案

您应该检查有效的十六进制或颜色名称。此解决方案基于两个答案，并牢记在心：

Javascript function to convert color names to hex codes
How to check if a string is a valid hex color representation?

function colorNameToHex(color) {
    var colors = {
        "aliceblue":"#f0f8ff","antiquewhite":"#faebd7","aqua":"#00ffff","aquamarine":"#7fffd4","azure":"#f0ffff","beige":"#f5f5dc","bisque":"#ffe4c4","black":"#000000","blanchedalmond":"#ffebcd","blue":"#0000ff","blueviolet":"#8a2be2","brown":"#a52a2a","burlywood":"#deb887","cadetblue":"#5f9ea0","chartreuse":"#7fff00","chocolate":"#d2691e","coral":"#ff7f50","cornflowerblue":"#6495ed","cornsilk":"#fff8dc","crimson":"#dc143c","cyan":"#00ffff","darkblue":"#00008b","darkcyan":"#008b8b","darkgoldenrod":"#b8860b","darkgray":"#a9a9a9","darkgreen":"#006400","darkkhaki":"#bdb76b","darkmagenta":"#8b008b","darkolivegreen":"#556b2f","darkorange":"#ff8c00","darkorchid":"#9932cc","darkred":"#8b0000","darksalmon":"#e9967a","darkseagreen":"#8fbc8f","darkslateblue":"#483d8b","darkslategray":"#2f4f4f","darkturquoise":"#00ced1","darkviolet":"#9400d3","deeppink":"#ff1493","deepskyblue":"#00bfff","dimgray":"#696969","dodgerblue":"#1e90ff","firebrick":"#b22222","floralwhite":"#fffaf0","forestgreen":"#228b22","fuchsia":"#ff00ff","gainsboro":"#dcdcdc","ghostwhite":"#f8f8ff","gold":"#ffd700","goldenrod":"#daa520","gray":"#808080","green":"#008000","greenyellow":"#adff2f","honeydew":"#f0fff0","hotpink":"#ff69b4","indianred":"#cd5c5c","indigo":"#4b0082","ivory":"#fffff0","khaki":"#f0e68c","lavender":"#e6e6fa","lavenderblush":"#fff0f5","lawngreen":"#7cfc00","lemonchiffon":"#fffacd","lightblue":"#add8e6","lightcoral":"#f08080","lightcyan":"#e0ffff","lightgoldenrodyellow":"#fafad2","lightgrey":"#d3d3d3","lightgreen":"#90ee90","lightpink":"#ffb6c1","lightsalmon":"#ffa07a","lightseagreen":"#20b2aa","lightskyblue":"#87cefa","lightslategray":"#778899","lightsteelblue":"#b0c4de","lightyellow":"#ffffe0","lime":"#00ff00","limegreen":"#32cd32","linen":"#faf0e6","magenta":"#ff00ff","maroon":"#800000","mediumaquamarine":"#66cdaa","mediumblue":"#0000cd","mediumorchid":"#ba55d3","mediumpurple":"#9370d8","mediumseagreen":"#3cb371","mediumslateblue":"#7b68ee","mediumspringgreen":"#00fa9a","mediumturquoise":"#48d1cc","mediumvioletred":"#c71585","midnightblue":"#191970","mintcream":"#f5fffa","mistyrose":"#ffe4e1","moccasin":"#ffe4b5","navajowhite":"#ffdead","navy":"#000080","oldlace":"#fdf5e6","olive":"#808000","olivedrab":"#6b8e23","orange":"#ffa500","orangered":"#ff4500","orchid":"#da70d6","palegoldenrod":"#eee8aa","palegreen":"#98fb98","paleturquoise":"#afeeee","palevioletred":"#d87093","papayawhip":"#ffefd5","peachpuff":"#ffdab9","peru":"#cd853f","pink":"#ffc0cb","plum":"#dda0dd","powderblue":"#b0e0e6","purple":"#800080","red":"#ff0000","rosybrown":"#bc8f8f","royalblue":"#4169e1","saddlebrown":"#8b4513","salmon":"#fa8072","sandybrown":"#f4a460","seagreen":"#2e8b57","seashell":"#fff5ee","sienna":"#a0522d","silver":"#c0c0c0","skyblue":"#87ceeb","slateblue":"#6a5acd","slategray":"#708090","snow":"#fffafa","springgreen":"#00ff7f","steelblue":"#4682b4","tan":"#d2b48c","teal":"#008080","thistle":"#d8bfd8","tomato":"#ff6347","turquoise":"#40e0d0","violet":"#ee82ee","wheat":"#f5deb3","white":"#ffffff","whitesmoke":"#f5f5f5","yellow":"#ffff00","yellowgreen":"#9acd32"
    };

    if (typeof colors[color.toLowerCase()] != 'undefined')
        return colors[color.toLowerCase()];

    return false;
}

function checkHex(color) {
    return /(^#[0-9A-F]{6}$)|(^#[0-9A-F]{3}$)/i.test(color);
}

var color = color1.value;

if (checkHex(color) || colorNameToHex(color)) {
    ctx.fillStyle = color;
} else {
    ctx.fillStyle = "#000000";
}

这篇关于如果颜色值无效-JavaScript的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持编程学习网！