node.js 变量范围

Question

I havethe following exported object:

module.exports = {
    value: 0,

    startTimer: function() {
        setInterval(function() {
            value++;
        }, 1000);
    }
}

How can I access value from that setInterval function? Thanks in advance.

Answer 1

You can either specify the full path to the value:

module.exports = {
    value: 0,

    startTimer: function() {
        setInterval(function() {
            module.exports.value++;
        }, 1000);
    }
}

Or, if you bind the function called by setTimeout to this , you can use this :

module.exports = {
    value: 0,

    startTimer: function() {
        setInterval(function() {
            this.value++;
        }.bind(this), 1000);
    }
}

This is similar to code like this, which you will see from time to time:

module.exports = {
    value: 0,

    startTimer: function() {
        var self = this;
        setInterval(function() {
            self.value++;
        }, 1000);
    }
}