JS 常用函数

HEX 和 RGB 的相互转换

function hexToRgb(hex) {
    // Expand shorthand form (e.g. '03F') to full form (e.g. '0033FF')
    var shorthandRegex = /^#?([a-f\d])([a-f\d])([a-f\d])$/i;
    hex = hex.replace(shorthandRegex, function(m, r, g, b) {
        return r + r + g + g + b + b;
    });

    var result = /^#?([a-f\d]{2})([a-f\d]{2})([a-f\d]{2})$/i.exec(hex);
    return result ? {
        r: parseInt(result[1], 16),
        g: parseInt(result[2], 16),
        b: parseInt(result[3], 16)
    } : null;
}
/*
 * 支持以下三种写法
 * 执行 console.log(hexToRgb('fc0'));
 * 执行 console.log(hexToRgb('ffcc00'));
 * 执行 console.log(hexToRgb('#ffcc00'));
 * 输出 {r: 255, g: 204, b: 0}
 */

function rgbToHex(r, g, b) {
  return '#'+ ((1 << 24) + (r << 16) + (g << 8) + b).toString(16).slice(1);
}
/*
 * 执行 console.log(rgbToHex(255, 204, 0);
 * 输出 #ffcc00
 */

获取小数点后的位数

function countDecimals(value) {
    if(Math.floor(value) === value) return 0;
    return value.toString().split('.')[1].length || 0; 
}
/*
 * 执行 console.log(countDecimals(1.234);
 * 输出 3
 */

获取 URL 参数

function getQueryString(name) {
    var reg = new RegExp('(^|&)' + name + '=([^&]*)(&|$)', 'i');
    var r = window.location.search.substr(1).match(reg);
    if (r != null) {
        return decodeURIComponent(r[2]);
    }
    return null;
}
/*
 * 例如 https://futurama.ink/wordpress?author=convict
 * 执行 console.log(getQueryString('author');
 * 输出 convict
 */

获取数组中的最大值

var data = [1, 2, 4, 5, 10];
console.log(Math.max(...data));

移动端设备的判断

function isMobile() {
    var _isMobile = false;
    (function(a) {
        if (/(android|bb\d+|meego).+mobile|avantgo|bada\/|blackberry|blazer|compal|elaine|fennec|hiptop|iemobile|ip(hone|od)|iris|kindle|lge |maemo|midp|mmp|mobile.+firefox|netfront|opera m(ob|in)i|palm( os)?|phone|p(ixi|re)\/|plucker|pocket|psp|series(4|6)0|symbian|treo|up\.(browser|link)|vodafone|wap|windows ce|xda|xiino/i.test(a) || /1207|6310|6590|3gso|4thp|50[1-6]i|770s|802s|a wa|abac|ac(er|oo|s\-)|ai(ko|rn)|al(av|ca|co)|amoi|an(ex|ny|yw)|aptu|ar(ch|go)|as(te|us)|attw|au(di|\-m|r |s )|avan|be(ck|ll|nq)|bi(lb|rd)|bl(ac|az)|br(e|v)w|bumb|bw\-(n|u)|c55\/|capi|ccwa|cdm\-|cell|chtm|cldc|cmd\-|co(mp|nd)|craw|da(it|ll|ng)|dbte|dc\-s|devi|dica|dmob|do(c|p)o|ds(12|\-d)|el(49|ai)|em(l2|ul)|er(ic|k0)|esl8|ez([4-7]0|os|wa|ze)|fetc|fly(\-|_)|g1 u|g560|gene|gf\-5|g\-mo|go(\.w|od)|gr(ad|un)|haie|hcit|hd\-(m|p|t)|hei\-|hi(pt|ta)|hp( i|ip)|hs\-c|ht(c(\-| |_|a|g|p|s|t)|tp)|hu(aw|tc)|i\-(20|go|ma)|i230|iac( |\-|\/)|ibro|idea|ig01|ikom|im1k|inno|ipaq|iris|ja(t|v)a|jbro|jemu|jigs|kddi|keji|kgt( |\/)|klon|kpt |kwc\-|kyo(c|k)|le(no|xi)|lg( g|\/(k|l|u)|50|54|\-[a-w])|libw|lynx|m1\-w|m3ga|m50\/|ma(te|ui|xo)|mc(01|21|ca)|m\-cr|me(rc|ri)|mi(o8|oa|ts)|mmef|mo(01|02|bi|de|do|t(\-| |o|v)|zz)|mt(50|p1|v )|mwbp|mywa|n10[0-2]|n20[2-3]|n30(0|2)|n50(0|2|5)|n7(0(0|1)|10)|ne((c|m)\-|on|tf|wf|wg|wt)|nok(6|i)|nzph|o2im|op(ti|wv)|oran|owg1|p800|pan(a|d|t)|pdxg|pg(13|\-([1-8]|c))|phil|pire|pl(ay|uc)|pn\-2|po(ck|rt|se)|prox|psio|pt\-g|qa\-a|qc(07|12|21|32|60|\-[2-7]|i\-)|qtek|r380|r600|raks|rim9|ro(ve|zo)|s55\/|sa(ge|ma|mm|ms|ny|va)|sc(01|h\-|oo|p\-)|sdk\/|se(c(\-|0|1)|47|mc|nd|ri)|sgh\-|shar|sie(\-|m)|sk\-0|sl(45|id)|sm(al|ar|b3|it|t5)|so(ft|ny)|sp(01|h\-|v\-|v )|sy(01|mb)|t2(18|50)|t6(00|10|18)|ta(gt|lk)|tcl\-|tdg\-|tel(i|m)|tim\-|t\-mo|to(pl|sh)|ts(70|m\-|m3|m5)|tx\-9|up(\.b|g1|si)|utst|v400|v750|veri|vi(rg|te)|vk(40|5[0-3]|\-v)|vm40|voda|vulc|vx(52|53|60|61|70|80|81|83|85|98)|w3c(\-| )|webc|whit|wi(g |nc|nw)|wmlb|wonu|x700|yas\-|your|zeto|zte\-/i.test(a.substr(0, 4))) {
            _isMobile = true;
        }

        if (isIOS() || isTablet()) {
            _isMobile = true;
        }
    })(window.navigator.userAgent || window.navigator.vendor || window.opera);

    return _isMobile;
}

function isTablet(mockUserAgent) {
    var userAgent = mockUserAgent || window.navigator.userAgent;
    return /ipad|Nexus (7|9)|xoom|sch-i800|playbook|tablet|kindle/i.test(userAgent);
}

function isIOS() {
    return /iPad|iPhone|iPod/.test(window.navigator.platform);
}

function isLandscape() {
    var orientation = window.orientation;
    return orientation === 90 || orientation === -90;
};

是否支持 WebP

/*
 * 方法一
 */
function checkWebp() {
	try{
		return (document.createElement('canvas').toDataURL('image/webp').indexOf('data:image/webp') == 0);
	}catch(err) {
		return  false;
	}
}

/*
 * 方法二
 */
var image = new Image();
// 图片加载完成时候的操作
image.onload = function() {
	// 图片加载成功且宽度为1，那么就代表支持webp了，因为这张base64图是webp格式。如果不支持会触发image.error方法
	if (image.width == 1) {
		// 支持
	}
	else {
		// 不支持
	}
}

// 一张支持alpha透明度的webp的图片，使用base64编码
image.src = 'data:image/webp;base64,UklGRkoAAABXRUJQVlA4WAoAAAAQAAAAAAAAAAAAQUxQSAwAAAARBxAR/Q9ERP8DAABWUDggGAAAABQBAJ0BKgEAAQAAAP4AAA3AAP7mtQAAAA==';

JS 常用函数

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