uniapp调用h5 api 解决 plus is undefined

使用条件编译，如调用cemera
// #ifdef APP-PLUS
var cmr = plus.camera.getCamera(2);
cmr.captureImage(function§ {
plus.io.resolveLocalFileSystemURL(p, function(entry) {
compressImage(entry.toLocalURL(),entry.name);
}, function(e) {
plus.nativeUI.toast(“读取拍照文件错误：” + e.message);
});
}, function(e) {
}, {
filter: ‘image’
});
// #endif