error undefined slash cmd

async initSlash(app) {
        let client = app.client;
        let arrayOfSlashCommands = [];
        client.slash?.forEach(f => {
            arrayOfSlashCommands.push(f);
        })
        console.log(arrayOfSlashCommands);
        if(client.testingServerID) {
            console.log(client.guilds.cache)
            // client.guilds.cache
            // .get(client.testingServerID)
            // .commands.set(arrayOfSlashCommands);
        } else {
            client.application.commands.set(arrayOfSlashCommands);
        }
    }

/**
     * All init in one function.
     */
    init(app, db) {
        app.client.on('messageCreate', async message => { this.handleCommand(app, message) });
        this.handleEvent(app);
        this.initSlash(app);
        app.client.on("interactionCreate", async interactions => { 
            if (interactions.isCommand()) { this.handleSlash(app, interactions) } else { this.createInteraction(app, interactions) } 
        })
        this.dbInit(db).then(app.client.log ? log : '');
    }

async initSlash(app) {
        let client = app.client;
        let arrayOfSlashCommands = [];
        client.slash?.forEach(f => {
            arrayOfSlashCommands.push(f);
        })
        console.log(arrayOfSlashCommands);
        if(client.testingServerID) {
            console.log(client.guilds.cache)
            // client.guilds.cache
            // .get(client.testingServerID)
            // .commands.set(arrayOfSlashCommands);
        } else {
            client.application.commands.set(arrayOfSlashCommands);
        }
    }

/**
     * All init in one function.
     */
    init(app, db) {
        app.client.on('messageCreate', async message => { this.handleCommand(app, message) });
        this.handleEvent(app);
        this.initSlash(app);
        app.client.on("interactionCreate", async interactions => { 
            if (interactions.isCommand()) { this.handleSlash(app, interactions) } else { this.createInteraction(app, interactions) } 
        })
        this.dbInit(db).then(app.client.log ? log : '');
    }