Initialize the `$refs` value

@inner
function initRefs() {
    this.$refs = {};

    let refInfo = this.props && this.props[REF_DATA_ATTR];
    let pageInstance = this.$page || this;
    let refComponents = pageInstance.__refComponents /* istanbul ignore next */ || {};
    pageInstance.__refComponents = refComponents;

    if (refInfo) {
        if (refInfo.charAt(0) === '[') {
            refComponents[refInfo] /* istanbul ignore next */ || (refComponents[refInfo] = []);
            refComponents[refInfo].push(this);
        }
        else {
            refComponents[refInfo] = this;
        }
    }

    let refs = this.$rawRefData;
    if (typeof refs === 'function') {
        refs = refs();
    }

    if (!refs) {
        return;
    }

    let result = {};
    Object.keys(refs).forEach(id => {
        result[id] = {
            get() {
                let value = refs[id];
                let isSelectAll = Array.isArray(value);
                isSelectAll && (value = value[0]);
                let key = isSelectAll ? `[]${value}` : value;
                let result = refComponents[key];
                isSelectAll && !result && (result = []);
                return result;
            },
            enumerable: true
        };
    });

    Object.defineProperties(this.$refs, result);
}