Using Open File Dialog in Cocos Creator project 详细步骤参考 https://xmanyou.com/cocos-creator-open-file-box/

FileBox.ts

// 影子工作室为你提供详细步骤 https://xmanyou.com/cocos-creator-open-file-box/

const {ccclass, property} = cc._decorator;

@ccclass
export default class FileBox extends cc.Component {
    // LIFE-CYCLE CALLBACKS:
    @property
    containerId = "_filebox_container_";
    @property
    inputBoxId = "_filebox_input_";

    inputBox = null;
    start () {
        this.initInputBox();
    }

    initInputBox(){
        let inputBox = this.getInputBox(this.inputBoxId, this.containerId);
        if(inputBox){
            inputBox.onchange = (evt)=>{
                console.info("===> input value change: ", evt);
                const fileList = evt.target.files;
                console.info("===> file list: ", fileList);
                console.info("===> value: ", inputBox.value);

                let file = fileList[0];
                if(!file){
                    console.info("===> No file selected");
                    return;
                }
                this.readFile(file);
            };
        }else{
            console.warn("Can't get or create input box");
        }
    }

    getInputBox(inputBoxId:string, containerId:string){
        if(!this.inputBox){
            let inputBox = document.getElementById(inputBoxId) as HTMLInputElement;
            if(!inputBox){
                let container = document.getElementById(containerId);
                if(!container){
                    container = document.createElement('div');
                    document.body.appendChild(container);
                    container.id = containerId;
                }

                inputBox = document.createElement("input") as HTMLInputElement;
                inputBox.id = inputBoxId;

                inputBox.type = "file";

                container.appendChild(inputBox);
            }
            this.inputBox = inputBox;
        }
        return this.inputBox;
    }

    onClick(){
        if(this.inputBox){
            console.info("click start");
            this.inputBox.click();
            console.info("click done")

        }
    }

    readFile(fileUrl){
        let reader = new FileReader();
        reader.onload = function(e) {
            let content = e.target.result;
            // Display file content
            console.info("===> file content: ", content);
        };
        // 这里用文本方式读，也可以用别的方式
        reader.readAsText(fileUrl);
    }
}

《Cocos Creator 项目中如何使用系统的文件选择对话框？》

It's not working on iOS safari.

OK...I only tested on Chrome on my MacOS.