11.Stock-based compensation

The Company measures stock-based compensation expense on the grant date, based on the fair value of the award, and recognizes the expense on a straight-line basis over the requisite service period for awards expected to vest. The Company estimated the grant date fair value of stock options using a Black-Scholes valuation model using the following weighted-average assumptions for the periods indicated:

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The Company granted 248 and 97 stock options during the 26 weeks ended August 1, 2020 and August 3, 2019, respectively. The stock-based compensation expense for stock options was $2,872 and $2,199 for the 13 weeks ended August 1, 2020 and August 3, 2019, respectively. The stock-based compensation expense for stock options was $5,347 and $4,319 for the 26 weeks ended August 1, 2020 and August 3, 2019, respectively. The weighted-average grant date fair value of these stock options was $54.40 and $89.91 for the 26 weeks ended August 1, 2020 and August 3, 2019, respectively. At August 1, 2020, there was approximately $23,696 of unrecognized stock-based compensation expense related to unvested stock options.

The Company issued 158 and 47 restricted stock units during the 26 weeks ended August 1, 2020 and August 3, 2019, respectively. The stock-based compensation expense for restricted stock units was $5,161 and $3,422 for the 13 weeks ended August 1, 2020 and August 3, 2019, respectively. The stock-based compensation expense for restricted stock units was $9,348 and $6,243 for the 26 weeks ended August 1, 2020 and August 3, 2019, respectively. At August 1, 2020, there was approximately $38,743 of unrecognized stock-based compensation expense related to restricted stock units.

The Company did not issue any performance-based restricted stock units during the 26 weeks ended August 1, 2020. The Company issued 21 performance-based restricted stock units during the 26 weeks ended August 3, 2019. The stock-based compensation expense for performance-based restricted stock units was $380 and $1,390 for the 13 weeks ended August 1, 2020 and August 3, 2019, respectively. The stock-based compensation benefit for performance-based restricted stock units was $100 for the 26 weeks ended August 1, 2020. The stock-based compensation expense for performance-based restricted stock units was $3,101 for the 26 weeks ended August 3, 2019. At August 1, 2020, there was approximately $1,019 of unrecognized stock-based compensation expense related to performance-based restricted stock units.