语法

Math.abs(x) // 必需。必须是一个数值。

示例

<script type="text/javascript">
document.write(Math.abs(7.25) + "<br />")
document.write(Math.abs(-7.25) + "<br />")
document.write(Math.abs(7.25-10))
</script>

输出：

7.25
7.25
2.75

在项目中使用的方法 上传图片

Init: function(up, file) {
    let alertMsg = cbFilesAddedParam.alertMsg;
    plupload.addFileFilter("img_ratio", function(ratio, file, cb) {
        if (file.type.indexOf("image") == -1) return cb(false);
        var originFile = file.getNative();
        var reader = new FileReader();
        var image = new Image();
        reader.readAsDataURL(originFile);
        reader.onload = function(_file) {
            image.src = _file.target.result;
            image.onload = function() {
                var meta = {
                    width: this.width,
                    height: this.height,
                    src: this.src
                };
                var compat = Math.abs((meta.width / meta.height) - ratio.ratio) < 0.01;
                cb(compat);
                compat || layer.alert(ratio.alertMsg);
            };
        };
    });
}

关键代码

reader.onload = function(_file) {
    image.src = _file.target.result;
    image.onload = function() {
        var meta = {
            width: this.width,
            height: this.height,
            src: this.src
        };
        var compat = Math.abs((meta.width / meta.height) - ratio.ratio) < 0.01;
        cb(compat);
        compat || layer.alert(ratio.alertMsg);
    };
};

精确代码

var compat = Math.abs((meta.width / meta.height) - ratio.ratio) < 0.01;

链接: https://fly63.com/article/detial/6490