我在React.js中编写for循环遇到麻烦

Question

I'm new to programming and I'm learning Facebook's react.js. I found a website that has a tutorial which builds a "shopping cart" using react. I tried to modify it to add more items using a for loop but it keeps giving me "unexpected token }" errors followed by this error:

"Invariant Violation: FluxProduct.render(): A valid ReactComponent must be returned. You may have returned undefined, an array or some other invalid object."

I realize there is a similar question that was answered but it didn't help me.

There is quite a bit of code in this project but the particular spot I'm having trouble with looks like this:

render: function() {
    var rows = [];
    var ats = (this.props.selected.sku in this.props.cartitems) ?
      this.props.selected.inventory - this.props.cartitems[this.props.selected.sku].quantity :
      this.props.selected.inventory;
    for (var i=0; i<2; i++){<div className="flux-products">
        <img src={'img/' + this.props.product.image}/>
        <div className="flux-products-detail">
          <h1 className="name">{this.props.product.name}</h1>
          <p className="description">{this.props.product.description}</p>
          <p className="price">Price: ${this.props.selected.price}</p>
          <select onChange={this.selectVariant}>
            {this.props.product.variants.map(function(variant, index){
              return (
                <option key={index} value={index}>{variant.type}</option>
              )
            })}
          </select>
          <button type="button" onClick={this.addToCart} disabled={ats  > 0 ? '' : 'disabled'}>
            {ats > 0 ? 'Add To Cart' : 'Sold Out'}
          </button>
        </div>
      </div>}
    return ("flux-products-detail"

    );
  },

});

If you want/need the original code and the rest of the project I'd be more than happy to provide it.

Answer 1

It looks like you are trying to compose three components in the for loop. However the result of the for loop is not stored to a variable, and not rendered properly in the return function.

// Use a variable to store the result of the loop
return (
  <div>
    {myComponent}
  </div>
)

Answer 2

In the case of using a loop to generate content for a React element, I usually formulate it something like this:

render: function() {

var items = [];
for(var i = 0; i < this.state.listOfItems.length; i++) {
    items.push( <ItemComponent value={this.state.listOfItems[i].value} />
}

return ( <div> {items} </div>)
};

So what you need to do is return from render some JSX for react to Render. as @FelixKling said, JSX isn't magic, you're essentially just returning a bunch of React.createElement functions.