Method preloadOneImg

Pagetual/pagetual.user.js:7121–7142

(src)

        }

        preloadOneImg(src) {
            return new Promise(resolve => {
                let img = document.createElement('img');
                img.src = src;
                this.preloadDiv.appendChild(img);
                if (img.complete) resolve('complete');
                else {
                    img.onload = e => {
                        resolve('load');
                    };
                    img.onerror = e => {
                        resolve('error');
                    };
                }
            }).then(e => {
                let src = this.unCheckedImgs.shift();
                if (src) {
                    this.preloadOneImg(src);
                }
                return e;
            });
        }

        preloadImageHandler() {
            if (this.preloadingImage || !this.unCheckedImgs.length) return;